Xp11 translocation renal cell carcinoma (RCC): extended immunohistochemical profile emphasizing novel RCC markers

MiT family translocation-associated renal cell carcinoma: A report of two cases in children

ABSTRACT

Renal cell carcinoma is uncommon in children and must be distinguished from the more common Wilms' tumor. Here, we present two cases of renal cell carcinoma in children both of whom presented with hematuria. Accurate diagnosis is essential in order to differentiate it from epithelial predominant Wilms' tumor which has vastly different prognosis and treatment. Immunohistochemistry for TFE3 is useful in establishing the diagnosis.

Establishment of a new prognostic risk model of GNG7 pathway-related molecules in clear cell renal cell carcinoma based on immunomodulators

Clear cell renal cell carcinoma (CCRCC) is a common tumor of the urological system for which surgery is the preferred treatment, but there is a lack of therapeutic options after surgery. This study aims to explore the biological role of GNG7 on CCRCC from a genetic perspective. Differences in mRNA expression and patient survival of GNG7 in patients with CCRCC and healthy patients were analyzed using the TCGA database. It was observed that GNG7 gene expression was downregulated in CCRCC tissue compared with healthy tissue, and high GNG7 predicted better prognosis for patients, and GNG7 also showed strong variability in clinical and TMN staging. The immune relevance of GNG7 and related genes was explored using renal cancer data from CCLE and TISIDB database. It was verified that the risk score constructed by 7 GNG7-related regulators might be used as an independent prognostic risk factor for CCRCC. A CCRCC prognostic model that involved 7 immune genes was further established to predict the survival probabilities of patients. At last, the GEO database and immunochemical tissue staining were used to validate GNG7 expression in CCRCC. Our study proposed a novel panel of genes to predict CCRCC OS based on GNG7-related immune genes, which may help to accurately predict the prognosis of CCRCC patients and make better clinical decisions for individual treatment.

Papillary Renal Cell Carcinoma: A Review of Prospective Clinical Trials

OPINION STATEMENT

PRCC is a unique histologic entity compared to other forms of renal cell carcinoma, harboring distinct molecular drivers. The WHO 2022 classification is further emphasizing the molecular biology by making molecular classifications of PRCC subclassifications and discontinuing the morphologic type 1 and type 2 classification system. We agree with this functional classification system and encourage all future clinical trials to only include patients with similar diagnosis instead of conducting basket trials (including all nccRCC together) which limits the scientific value of those conclusions. Based on recent disease-specific clinical trial (S1500, PAPMET), the current standard of care for patients with treatment naïve PRCC is cabozantinib. Prospective clinical trials clearly establish that immune checkpoint inhibitor therapy has meaningful activity in PRCC. The data to date include only single-arm clinical trials of combination immune therapy. Despite the positive and encouraging results, we need validation through randomized studies because of the overestimation of effect size seen in single-arm trials. These randomized trials are currently underway and enrolling. We strongly encourage all physicians to support these studies and enroll patients with PRCC to these trials in order to continue improving the standard of care.

Vascular Expression of Prostate-specific Membrane Antigen (PSMA) in MiTF Family Translocation Renal Cell Carcinoma and Related Neoplasms

Multiple studies have demonstrated prostate-specific membrane antigen (PSMA) expression in the neo-vasculature of non-prostate tumors including clear cell renal cell carcinoma (ccRCC). However, PSMA expression in rare renal tumors including MiTF family translocation renal cell carcinoma has not been previously characterized. We examined PSMA expression by immunohistochemistry in a series of MiTF family translocation renal cell carcinomas as well as in several genetically related tumors including alveolar soft part sarcoma and PEComas with TFE3 rearrangements. PSMA expression was also studied in several cases of ccRCC and papillary RCC. Overall, PSMA immunohistochemistry was performed in 61 samples from 58 patients. Vascular PSMA expression was seen with the highest frequency in ccRCC [88% (14/16)] (38% focal, 50% diffuse). Translocation RCC (tRCC) demonstrated the second highest frequency of PSMA expression [71% (22/28)] (57% focal, 14% diffuse), followed by alveolar soft part sarcoma [50% (4/8)] (38% focal, 12% diffuse). No PSMA expression was seen in PEComas with TFE3 rearrangement (0/3) or papillary RCC (0/6). PSMA expression was only present in tumor-associated neo-vasculature. A patient with oligometastatic tRCC underwent 68 Ga-PSMA-11 PET imaging which detected multiple putative metastatic lesions not detected on conventional computed tomography imaging performed 2 weeks prior, supporting the potential utility of PSMA imaging in tRCC. These findings have potential implications for the utility of PSMA guided diagnostic and therapeutic agents in both common and uncommon renal cell carcinoma subtypes as well as genetically related mesenchymal neoplasms.

Clinicopathological correlation of Cathepsin K expression in salivary gland carcinomas; relation to patients` outcome

BACKGROUND

Salivary gland carcinomas (SGCs) represent various groups of tumors that demonstrate marked diversity in their prognosis owing to different histology and clinical characteristics. One of the poor prognostic indicators is distant metastasis which is considered the major reason for death in SGC patients. Discovering new biomarkers is urgently required to aid in the detection of cancer onset and progression. Cathepsin K (CTSK), the lysosomal cysteine protease has a principal role in cancer invasion and progression through interaction with the tumor microenvironment, degradation of extracellular membrane proteins and destruction of the elastic lamina of blood vessels. In the English literature, little information was present about the role of CTSK in SGCs. The current study aimed to assess the immunohistochemical expression of CTSK in SGCs and correlate its expression to different clinicopathologic parameters.

METHODS

The retrospective study applied to 45 cases of SGCs categorized as high-grade (33 cases) and low-grade SGCs (12 cases) following the criteria of WHO classification (2017) of head and neck tumors. All patients` clinicopathological and follow-up records were retrieved. The following statistical tests were used to study the variance of CTSK expression in SGCs concerning different clinicopathological parameters; Pearson`s Chi-square test, unpaired two-tailed student t-test, One-way ANOVA, and Post Hoc tests. Disease-free survival (DFS) and Overall survival (OS) were calculated and displayed with the Kaplan-Meier strategy and analyzed with the log-rank test. Univariate and multivariate survival analyses were performed with Cox regression. A P-value lesser than 0.05 was considered statistically significant.

RESULTS

Strong CTSK expression was significantly related to high-grade SGCs (P = 0.000), large infiltrating carcinomas (P = 0.000), presence of nodal (P = 0.041) and distant metastasis (P = 0.009), advanced TNM clinical stage (P = 0.000), the incidence of recurrence (P = 0.009), and reduced DFS (P = 0.006). Distant metastasis was the independent predictor for DFS using Cox regression model.

CONCLUSIONS

CTSK has a great role in cancer progression by triggering many signaling pathways. Its level in cancerous tissue is considered an effective index for predicting the severity and prognosis of cancer. Therefore, we indicate its utility as a prognostic tool and therapeutic target for cancer treatment.

TRIAL REGISTRATION

Retrospectively registered.

TFE3 gene rearrangement and protein expression contribute to a poor prognosis of renal cell carcinoma

Background

TFE3-rearranged renal cell carcinoma (TFE3-rearranged RCC) is a type of kidney cancer with a low incidence, with no consensus about whether it has a worse prognosis than clear cell renal cell carcinoma (ccRCC). This study attempted to elucidate the impact of TFE3-rearranged RCC by analyzing its clinical features and prognosis.

Methods

Patients treated in Sun Yat-sen Memorial Hospital (SYSMH) who were suspected to be diagnosed with TFE3-rearranged RCC were divided into two groups, TFE3-rearranged RCC and ccRCC with positive TFE3 protein expression on immunohistochemistry [TFE3(+) ccRCC], by dual-color, break-apart fluorescence in situ hybridization (FISH). After balancing the baseline characteristics with TFE3(+) ccRCC using the propensity score matching (PSM) method in a ratio of 2, we selected patients diagnosed with ccRCC with negative TFE3 protein expression on immunohistochemistry [TFE3(-) ccRCC]. The impact of TFE3 gene rearrangement and protein expression on renal cell carcinoma was determined by feature comparison with a nonparametric test and survival analysis with the Kaplan‒Meier method.

Results

Among 37 patients suspected of having TFE3-rearranged RCC, 13 patients were diagnosed with TFE3-rearranged RCC, and 24 patients had TFE3(+) ccRCC. The recurrence and new metastasis of TFE3-rearranged RCC was relatively common, even if the tumor stage was early at the first diagnosis. Through feature comparison and survival analysis, we found that TFE3-rearranged RCC was quite similar to TFE3(+) ccRCC. Compared with TFE3(-) ccRCC, TFE3(+) ccRCC tended to have a larger tumor diameter (P = 0.011), higher neutrophil/lymphocyte ratio (NLR) (P = 0.017) and metastatic potential (P = 0.022), and worse overall survival (OS) (P = 0.043) and PFS (P = 0.016). The survival analysis showed that TFE3-rearranged RCC had a worse PFS than ccRCC (P = 0.002), and TFE3(+) RCC had a worse PFS than TFE3(-) RCC (P = 0.001). According to the stratification system based on the combination of TFE3 and lymphovascular invasion (LVI), we further found that the prognosis from good to poor was TFE3(-) LVI(-), TFE3(+) LVI(-), TFE3(+) LVI(+) and TFE3(-) LVI(+), with statistically significant differences in both OS (P = 0.001) and PFS (P < 0.001). In addition, we also reported two cases with poor prognosis, of which one was TFE3-rearranged RCC and the other was TFE3(+) ccRCC.

Conclusions

This is a novel finding that both FISH confirmed TFE3 gene rearrangement-mediated TFE3-rearranged RCC and IHC confirmed positive TFE3 protein expression [TFE3(+)] contribute to a poor prognosis in RCC, suggesting more active treatment and careful follow-up for TFE3(+) RCC patients. The combination of TFE3 and LVI may be a new risk stratification system for RCC.

Clear cell renal cell carcinoma with focal psammomatous calcifications: a rare occurrence mimicking translocation carcinoma

AIMS

Renal cell carcinoma (RCC) with clear cells and psammoma-like calcifications would often raise suspicion for MITF family translocation RCC. However, we have rarely encountered tumours consistent with clear cell RCC that contain focal psammomatous calcifications.

METHODS AND RESULTS

We identified clear cell RCCs with psammomatous calcifications from multiple institutions and performed immunohistochemistry and fluorescence and RNA in-situ hybridisation (FISH and RNA ISH). Twenty-one tumours were identified: 12 men, nine women, aged 45-83 years. Tumour size was 2.3-14.0 cm (median = 6.75 cm). Nucleolar grade was 3 (n = 14), 2 (n = 4) or 4 (n = 3). In addition to clear cell pattern, morphology included eosinophilic (n = 12), syncytial giant cell (n = 4), rhabdoid (n = 2), branched glandular (n = 1), early spindle cell (n = 1) and poorly differentiated components (n = 1). Labelling for CA9 was usually 80-100% of the tumour cells (n = 17 of 21), but was sometimes decreased in areas of eosinophilic cells (n = 4). All (19 of 19) were positive for CD10. Most (19 of 20) were positive for AMACR (variable staining = 20-100%). Staining was negative for keratin 7, although four showed rare positive cells (four of 20). Results were negative for cathepsin K (none of 19), melan A (none of 17), HMB45 (none of 17), TFE3 (none of 5), TRIM63 RNA ISH (none of 13), and TFE3 (none of 19) and TFEB rearrangements (none of 12). Seven of 19 (37%) showed chromosome 3p deletion. One (one of 19) showed trisomy 7 and 17 without papillary features.

CONCLUSIONS

Psammomatous calcifications in RCC with a clear cell pattern suggests a diagnosis of MITF family translocation RCC; however, psammomatous calcifications can rarely be found in true clear cell RCC.

Cathepsin K: A Versatile Potential Biomarker and Therapeutic Target for Various Cancers

Cancer, a common malignant disease, is one of the predominant causes of diseases that lead to death. Additionally, cancer is often detected in advanced stages and cannot be radically cured. Consequently, there is an urgent need for reliable and easily detectable markers to identify and monitor cancer onset and progression as early as possible. Our aim was to systematically review the relevant roles of cathepsin K (CTSK) in various possible cancers in existing studies. CTSK, a well-known key enzyme in the bone resorption process and most studied for its roles in the effective degradation of the bone extracellular matrix, is expressed in various organs. Nowadays, CTSK has been involved in various cancers such as prostate cancer, breast cancer, bone cancer, renal carcinoma, lung cancer and other cancers. In addition, CTSK can promote tumor cells proliferation, invasion and migration, and its mechanism may be related to RANK/RANKL, TGF-β, mTOR and the Wnt/β-catenin signaling pathway. Clinically, some progress has been made with the use of cathepsin K inhibitors in the treatment of certain cancers. This paper reviewed our current understanding of the possible roles of CTSK in various cancers and discussed its potential as a biomarker and/or novel molecular target for various cancers.

Minimally invasive cytologic evaluation leading to the diagnosis of TFE3-rearranged renal cell carcinoma: A case report

TFE3-rearranged renal cell carcinoma (RCC) has been categorized as a molecularly defined renal carcinoma in the 2022 WHO classification of tumors as it does not demonstrate a specific genotype-phenotype correlation. However, in order to arrive at the diagnosis, recognition of the broad spectrum of cytologic and histologic features that can be seen in TFE3-rearranged RCC is important for differential diagnostic consideration. Reported here is the diagnostic workup of a TFE3-rearranged RCC using very limited tissue sample. The initial evaluation was dependent on the cytomorphologic findings observed on a touch preparation made from the renal mass biopsy, directing appropriate selection of ancillary tests, and leading to a definitive diagnosis.

TFE3 Rearrangement and Expression in Renal Cell Carcinoma

TFE3 rearranged Renal cell carcinoma (RCC) is not very common, and demonstrates unique heterogenous morphological features overlapping other recognized entities and distinct immunoprofile. It can be seen in any age group, therefore practicing pathologists should be aware of the distinctive clinical settings and histologic findings associated with these tumors and subsequently employ an adequate panel of ancillary studies in order to confirm the diagnosis. Recognizing these entities remains crucial for future clinical trials and development of novel therapies.

Liver Ischemia and Reperfusion Induce Periportal Expression of Necroptosis Executor pMLKL Which Is Associated With Early Allograft Dysfunction After Transplantation

Background

Early allograft dysfunction (EAD) following liver transplantation (LT) remains a major threat to the survival of liver grafts and recipients. In animal models, it is shown that hepatic ischemia-reperfusion injury (IRI) triggers phosphorylation of Mixed Lineage Kinase domain-like protein (pMLKL) inducing necroptotic cell death. However, the clinical implication of pMLKL-mediated cell death in human hepatic IRI remains largely unexplored. In this study, we aimed to investigate the expression of pMLKL in human liver grafts and its association with EAD after LT.

Methods

The expression of pMLKL was determined by immunohistochemistry in liver biopsies obtained from both human and rat LT. Human liver biopsies were obtained at the end of preservation (T0) and ~1 hour after reperfusion (T1). The positivity of pMLKL was quantified electronically and compared in rat and human livers and post-LT outcomes. Multiplex immunofluorescence staining was performed to characterize the pMLKL-expressing cells.

Results

In the rat LT model, significant pMLKL expression was observed in livers after IRI as compared to livers of sham-operation animals. Similarly, the pMLKL score was highest after IRI in human liver grafts (in T1 biopsies). Both in rats and humans, the pMLKL expression is mostly observed in the portal triads. In grafts who developed EAD after LT (n=24), the pMLKL score at T1 was significantly higher as compared to non-EAD grafts (n=40). ROC curve revealed a high predictive value of pMLKL score at T1 (AUC 0.70) and the ratio of pMLKL score at T1 and T0 (pMLKL-index, AUC 0.82) for EAD. Liver grafts with a high pMLKL index (>1.64) had significantly higher levels of serum ALT, AST, and LDH 24 hours after LT compared to grafts with a low pMLKL index. Multivariate logistical regression analysis identified the pMLKL-index (Odds ratio=1.3, 95% CI 1.1-1.7) as a predictor of EAD development. Immunohistochemistry on serial sections and multiplex staining identified the periportal pMLKL-positive cells as portal fibroblasts, fibrocytes, and a minority of cholangiocytes.

Conclusion

Periportal pMLKL expression increased significantly after IRI in both rat and human LT. The histological score of pMLKL is predictive of post-transplant EAD and is associated with early liver injury after LT. Periportal non-parenchymal cells (i.e. fibroblasts) appear most susceptible to pMLKL-mediated cell death during hepatic IRI.

Chameleon TFE3-translocation RCC and How Gene Partners Can Change Morphology: Accurate Diagnosis Using Contemporary Modalities

Translocation renal cell carcinoma (tRCC) with TFE3 gene rearrangements has been born as a distinct entity 20 years ago. These relatively rare tumors were notable among other RCC subtypes because of their disproportionally high incidence among children and young adults. Initial reports were focused on describing unifying morphologic criteria and typical clinical presentation. Follow-up studies of ancillary immunohistochemical and hybridization techniques provided additional diagnostic tools allowing recognition of tRCC tumors in practice. However, a growing body of literature also expanded the clinicomorphologic spectrum of tRCCs, to include a significant morphologic overlap with other RCC variants thus blurring the diagnostic clarity of this entity. More recent molecular studies utilizing next-generation sequencing technology accelerated recognition of numerous novel gene partners fusing at different breakpoints with the TFE3 gene. Accumulating data indicates that morphologic and clinical heterogeneity of tRCC could be explained by fusion subtypes, and knowledge of TFE3 partnering genes may be important in predicting tumor behavior. Herein we provided a comprehensive analysis of ∼400 tRCC cases with known TFE3 fusion partners, estimated their relative incidence and summarized clinicomorphologic features associated with most common fusion subtypes. Our data was based on an extensive literature review and had a special focus on comparing immunohistochemistry, fluorescent in situ hybridization and contemporary molecular studies for the accurate diagnosis of tRCC.

A review of neoplasms with MITF/MiT family translocations

Microphthalmia-associated transcription factor (MITF/MiT) family is a group of basic helix-loop-helix leucine zipper (bHLH-LZ) transcription factors including TFE3 (TFEA), TFEB, TFEC and MITF. The first renal neoplasms involving MITF family translocation were renal cell carcinomas with chromosome translocations involving ASPL-TFE3/t(X;17)(p11.23;q25) or MALAT1-TFEB/t(6;11)(p21.1;q12), and now it is known as MiT family translocation RCC in 2016 WHO classification. Translocations involving MITF family genes also are found in other tumor types, such as perivascular epithelioid cell neoplasm (PEComa), Alveolar soft part sarcoma (ASPS), epithelioid hemangioendothelioma, ossifying fibromyxoid tumor (OFMT), and clear cell tumor with melanocytic differentiation and ACTIN-MITF translocation. In this review, we summarize the features of different types of neoplasms with MITF family translocations.

Papillary Renal Cell Carcinoma With Microcystic Architecture Is Strongly Associated With Extrarenal Invasion and Metastatic Disease

Papillary renal cell carcinoma (PRCC) is well-recognized as a morphologically and molecularly heterogenous group of kidney tumors with variable clinical behavior. Our goal was to analyze a unique histologic pattern of PRCC we have observed in routine practice to evaluate for potential clinical significance or distinct molecular signature. We identified 42 cases of PRCC showing a morphologically distinct architecture characterized by numerous epithelial-lined cysts containing the papillary tumor (herein called "microcysts"), which are typically separated by fibrous stroma. Of the initial 42 case test set with microcystic features, 23 (55%) were stage pT3a or higher. Most tumors had strong and diffuse cytoplasmic immunoreactivity for CK7 (93%, 37/40) and AMACR (100%, 40/40). Fumarate hydratase staining was retained in all cases tested (39/39). We performed next-generation sequencing on 15 of these cases with available tissue and identified chromosomal alterations commonly reported in historically "type 1" PRCC, notably multiple chromosomal gains, particularly of chromosomes 7 and 17, and MET alterations. However, alterations in pathways associated with more aggressive behavior (including SETD2, CDKN2A, and members of the NRF pathway) were also identified in 6 of 15 cases tested (40%). Given this molecular and immunophenotypic data, we subsequently reviewed an additional group of 60 consecutive pT2b-pT3 PRCCs to allow for comparisons between cases with and without microcysts, to assess for potential associations with other recently described histologic patterns (ie, "unfavorable architecture": micropapillary, solid, and hobnail), and to assess interobserver reproducibility for diagnosing architectural patterns and grade. Of the total combined 102 PRCCs, 67 (66%) had microcystic architecture within the intrarenal component but were commonly admixed with other patterns (39% had micropapillary, 31% solid, and 31% hobnail). Twenty-seven cases (26%) had metastatic disease, and 24 of these 27 (89%) had microcystic architecture in the intrarenal tumor. Within the pT3 subset, 21 of 22 cases with metastases (95%) had extrarenal invasion as either individual microcysts in renal sinus fat or aggregates of microcysts bulging beyond the confines of the capsule. Backward elimination and stepwise regression methods to detect features significantly associated with adverse outcome identified solid architecture (hazard ratio [HR]: 6.3; confidence interval [CI]: 2.1-18.8; P=0.001), hobnail architecture (HR: 5.3; CI: 1.7-16.7; P=0.004), and microcystic architecture at the tumor-stromal interface (HR: 4.2; CI: 1.1-16.7; P=0.036) as strongest. Of architectural patterns and grade, the microcystic pattern had a substantial interobserver agreement (κ score=0.795) that was highest among the 6 observers. In summary, PRCCs with microcystic architecture represents a subset of historically "type 1" PRCC with a predilection for morphologically distinctive extrarenal involvement and metastatic disease. Microcysts co-vary with other "unfavorable" architectural patterns also associated with higher risk for aggressive disease (ie, micropapillary, hobnail, and solid), but microcysts were more common and have superior interobserver reproducibility. These findings suggest that microcystic PRCC should be recognized as a potentially aggressive histologic pattern of growth in PRCC.

GPNMB expression identifies TSC1 /2/ mTOR ‐associated and MiT family translocation‐driven renal neoplasms

GPNMB (glycoprotein nonmetastatic B) and other TFE3/TFEB transcriptional targets have been proposed as markers for microphthalmia (MiT) translocation renal cell carcinomas (tRCCs). We recently demonstrated that constitutive mTORC1 activation via TSC1/2 loss leads to increased activity of TFE3/TFEB, suggesting that the pathogenesis and molecular markers for tRCCs and TSC1/2‐associated tumors may be overlapping. We examined GPNMB expression in human kidney and angiomyolipoma (AML) cell lines with TSC2 and/or TFE3/TFEB loss produced using CRISPR–Cas9 genome editing as well as in a mouse model of Tsc2 inactivation‐driven renal tumorigenesis. Using an automated immunohistochemistry (IHC) assay for GPNMB, digital image analysis was employed to quantitatively score expression in clear cell RCC (ccRCC, n = 87), papillary RCC (papRCC, n = 53), chromophobe RCC (chRCC, n = 34), oncocytoma (n = 4), TFE3‐ or TFEB‐driven tRCC (n = 56), eosinophilic solid and cystic RCC (ESC, n = 6), eosinophilic vacuolated tumor (EVT, n = 4), and low‐grade oncocytic tumor (LOT, n = 3), as well as AML (n = 29) and perivascular epithelioid cell tumors (PEComas, n = 8). In cell lines, GPNMB was upregulated following TSC2 loss in a MiT/TFE‐ and mTORC1‐dependent fashion. Renal tumors in Tsc2^+/− A/J mice showed upregulation of GPNMB compared with normal kidney. Mean GPNMB expression was significantly higher in tRCC than in ccRCC (p < 0.0001), papRCC (p < 0.0001), and chRCC (p < 0.0001). GPNMB expression in TSC1/2/MTOR alteration‐associated renal tumors (including ESC, LOT, AML, and PEComa) was comparable to that in tRCC. The immunophenotype of tRCC and TSC1/2/MTOR alteration‐associated renal tumors is highly overlapping, likely due to the increased activity of TFE3/TFEB in both, revealing an important caveat regarding the use of TFE3/TFEB‐transcriptional targets as diagnostic markers. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Case Report: TFE3 Positive Xp11.2 Translocation Renal Cell Carcinoma (TRCC) – A Case Study and Review of the Literature

Microphthalmia-associated transcription factor renal cell cancer, also known as translocation renal cell cancer, belongs to the group of extremely rare non-clear-cell kidney neoplasms. Their incidence is lower in adulthood than in childhood. The only known risk factor for the development of this tumor is prior chemotherapy. In the operable stage of the disease, the prognosis depends on the status of regional lymph nodes. Interestingly lymph node positivity worsens the prognosis only in the adult patient population. Radical surgical excision is the best therapy in the early stage. The optimal treatment strategy for locally advanced and metastatic disease has not been established, given the lack of evidence in such a rare disease. We present the case of a patient with an aggressive course of this neoplasm treated with temsirolimus, who achieved 10-month control of this neoplasm accompanied by a discussion on other therapeutic possibilities.

TFE3 and TFEB-rearranged renal cell carcinomas: an immunohistochemical panel to differentiate from common renal cell neoplasms

TFE3/TFEB-rearranged renal cell carcinomas are characterized by translocations involving TFE3 and TFEB genes. Despite the initial description of typical morphology, their histological spectrum is wide, mimicking common subtypes of renal cell tumors. Thus, the diagnosis is challenging requiring the demonstration of the gene rearrangement, usually by FISH. However, this technique is limited in most laboratories and immunohistochemical TFE3/TFEB analysis is inconsistent. We sought to identify a useful immunohistochemical panel using the most common available markers to recognize those tumors. We performed an immunohistochemical panel comparing 27 TFE3-rearranged and 10 TFEB-rearranged renal cell carcinomas to the most common renal cell tumors (150 clear cell, 100 papillary, 50 chromophobe renal cell carcinomas, 18 clear cell papillary renal cell tumors, and 50 oncocytomas). When dealing with neoplasms characterized by cells with clear cytoplasm, CA9 is a helpful marker to exclude clear cell renal cell carcinoma. GATA3, AMACR, and CK7 are useful to rule out clear cell papillary renal cell tumor. CK7 is negative in TFE3/TFEB-rearranged renal cell carcinoma and positive in papillary renal cell carcinoma, being therefore useful in this setting. Parvalbumin and CK7/S100A1 respectively are of paramount importance when TFE3/TFEB-rearranged renal cell carcinoma resembles oncocytoma and chromophobe renal cell carcinoma. Moreover, in TFEB-rearranged renal cell carcinoma, cathepsin K and melanogenesis markers are constantly positive, whereas TFE3-rearranged renal cell carcinoma stains for cathepsin K in roughly half of the cases, HMB45 in 8% and Melan-A in 22%. In conclusion, since TFE3/TFEB-rearranged renal cell carcinoma may mimic several histotypes, an immunohistochemical panel to differentiate them from common renal cell tumors should include cathepsin K, CA9, CK7, and parvalbumin.

Immunohistochemistry for the diagnosis of renal epithelial neoplasms

Despite the increasing number of newly identified renal neoplasms, the diagnosis of renal cell carcinoma (RCC) can usually be reached with careful histologic examination and a limited immunohistochemical (IHC) panel. Clear cell, papillary, chromophobe RCC and oncocytoma account for more than 90% of renal neoplasia in adults, and sophisticated ancillary tools are usually unnecessary. Renal tumors with entity-defining genetic alterations may ultimately require molecular confirmation via cytogenetics or sequencing technologies, such as RCC with TFE3, TFEB, or ALK gene rearrangements, or TFEB amplified RCC. In fumarate hydratase-deficient and succinate dehydrogenase-deficient RCC, highly specific IHC markers can strongly suggest the diagnosis. In the metastatic setting, PAX8 and carbonic anhydrase 9 are among the most helpful markers for confirming RCC and clear cell type, respectively; however, caution should be exercised in the absence of a current or historical renal mass. In diagnostically challenging cases, such as renal eosinophilic tumors with low-grade nuclear features, or infiltrative high-grade tumors, careful examination coupled with a judicious panel of IHC markers usually resolves the diagnosis. This review offers concise algorithms for diagnosis of kidney neoplasia with the latest recognized, provisional, and emerging entities to daily pathology practice.

A Novel NIPBL-NACC1 Gene Fusion Is Characteristic of the Cholangioblastic Variant of Intrahepatic Cholangiocarcinoma

We report a novel NIPBL-NACC1 gene fusion in a rare primary hepatic neoplasm previously described as the "cholangioblastic variant of intrahepatic cholangiocarcinoma." The 2 index cases were identified within our consultation files as morphologically distinctive primary hepatic neoplasms in a 24-year-old female and a 54-year-old male. The neoplasms each demonstrated varied architecture, including trabecular, organoid, microcystic/follicular, and infiltrative glandular patterns, and biphasic cytology with large, polygonal eosinophilic cells and smaller basophilic cells. The neoplasms had a distinctive immunoprofile characterized by diffuse labeling for inhibin, and patchy labeling for neuroendocrine markers (chromogranin and synaptophysin) and biliary marker cytokeratin 19. RNA sequencing of both cases demonstrated an identical fusion of NIBPL exon 8 to NACC1 exon 2, which was further confirmed by break-apart fluorescence in situ hybridization assay for each gene. Review of a tissue microarray including 123 cases originally diagnosed as well-differentiated neuroendocrine neoplasm at one of our hospitals resulted in identification of a third case with similar morphology and immunophenotype in a 52-year-old male, and break-apart fluorescence in situ hybridization probes confirmed rearrangement of both NIPBL and NACC1. Review of The Cancer Genome Atlas (TCGA) sequencing data and digital images from 36 intrahepatic cholangiocarcinomas (www.cbioportal.org) revealed one additional case with the same gene fusion and the same characteristic solid, trabecular, and follicular/microcystic architectures and biphasic cytology as seen in our genetically confirmed cases. The NIPBL-NACC1 fusion represents the third type of gene fusion identified in intrahepatic cholangiocarcinoma, and correlates with a distinctive morphology described herein.

Translocation carcinomas of the kidney

The MiT subfamily of transcription factors includes TFE3, TFEB, TFEC, and MITF. Gene fusions involving two of these transcription factors have been well-characterized in renal cell carcinoma (RCC). The TFE3-rearranged RCC (also known as Xp11 translocation RCC) was first officially recognized in the 2004 World Health Organization (WHO) renal tumor classification. The TFEB-rearranged RCC, which typically harbor a t(6;11)(p21;q12) translocation which results in a MALAT1-TFEB gene fusion, were first officially recognized in the 2016 WHO renal tumor classification. These two subtypes of translocation RCC have many similarities. Both disproportionately involve young patients, although adult translocation RCC overall outnumber pediatric cases. Both often have unusual and distinctive morphologies; the TFE3-rearranged RCCs frequently have clear cells with papillary architecture and abundant psammoma bodies, while the TFEB-rearranged RCCs frequently have a biphasic appearance with both small and large epithelioid cells and nodules of basement membrane material. However, the morphology of these two neoplasms can overlap, with one mimicking the other or other more common renal neoplasms. Both of these RCC underexpress epithelial immunohistochemical markers, such as cytokeratin and epithelial membrane antigen, relative to most other RCC. Unlike other RCC, both frequently express the cysteine protease cathepsin k and often express melanocytic markers like HMB45 and Melan A. Finally, TFE3 and TFEB have overlapping functional activity as these two transcription factors frequently heterodimerize and bind to the same targets. Therefore, these two neoplasms are now grouped together under the heading of "MiT family translocation RCC." Approximately 50 renal cell carcinomas with gene fusions involving the anaplastic lymphoma kinase (ALK) gene have now been reported. While those with a Vinculin-ALK fusion have distinctive features (predilection to affect children with sickle cell trait and to show solid architecture with striking cytoplasmic vacuolization), other ALK-fusion RCCs have more varied clinical presentations and pathologic features. This review summarizes our current knowledge of these recently described RCC.

Immunohistochemical expression of PAX8, PAX2, and cytokeratin in melanomas

BACKGROUND

Deviations from the classic melanocytic immunophenotype in melanoma can present a diagnostic challenge. PAX8 and PAX2 are common markers for renal or Müllerian differentiation. While most PAX8+ or PAX2+ carcinomas are seldom confused with melanoma, some cases may show a more ambiguous immunophenotype, especially when MiTF family altered renal cell carcinoma (MiTF-RCC) is in the differential diagnosis. Neither PAX8 nor PAX2 expression has been reported in melanoma to date. We aimed to better characterize PAX8, PAX2, and cytokeratin immunoreactivity in a large series of melanomas.

METHODS

Tissue microarrays consisting of 263 melanomas were immunostained for PAX8, PAX2, and cytokeratin and graded by an h-score.

RESULTS

PAX8 expression was seen in 7.9% of melanomas and was significantly associated with spindle cytomorphology. PAX2 was positive in one (0.4%) melanoma. Cytokeratin positivity was seen in three (1.2%) cases and was associated with metastases.

CONCLUSIONS

PAX8 is expressed in a subset of melanomas and may be strong/extensive. As PAX8 positivity does not exclude a diagnosis of melanoma, it should be used in conjunction with other immunohistochemical markers, such as cytokeratin and PAX2, when melanoma, MiTF-RCC, and other PAX8+ tumors are in the differential diagnosis.

mTOR Inhibition Increases Transcription Factor E3 (TFE3) Activity and Modulates Programmed Death-Ligand 1 (PD-L1) Expression in Translocation Renal Cell Carcinoma

The efficacy of programmed cell death protein ligand (PD-L)-1/PD-1 checkpoint blockade in renal cell carcinoma (RCC) remains unknown. The effects of mTOR inhibitors are uncertain, and patients may develop resistance to them. The limited understanding of cancer cell-intrinsic mTOR-mediated pathways remains a challenge in developing effective treatments. Whether transcription factor (TF)-E3 regulates PD-L1 expression and the tumor microenvironment was investigated, and the effects of an mammalian target of rapamycin (mTOR) inhibitor on translocation RCC were explored. TFE3 was overexpressed in clear cell RCC cell lines, and PD-L1 expression was analyzed by Western blot analysis. PD-L1 activity in relation to TFE3 expression in translocation RCC was also analyzed, via TFE3 knockdown and treatment with an mTOR inhibitor. The results were correlated with the gene expression profile, evaluated using digital multiplex analysis. TFE3 and PD-L1 expression were positively correlated in RCC cells. TFE3 overexpression was associated with the expression of PD-L1 in RCC. Furthermore, mTOR inhibition was associated with enhanced PD-L1 expression via TFE3 activation in translocation RCC. These data support the feasibility of combination therapy based on mTOR inhibition and PD-L1 blockade as a novel strategy for the treatment of patients with translocation RCC.

Autophagy in Xp11 translocation renal cell carcinoma: from bench to bedside

Xp11 translocation renal cell carcinoma (tRCC) characterized by the rearrangement of the TFE3 is recently identified as a unique subtype of RCC that urgently requires effective prevention and treatment strategies. Therefore, determining suitable therapeutic targets and fully understanding the biological significance of tRCC is essential. The importance of autophagy is increasingly acknowledged because it shows carcinogenic activity or suppressor effect. Autophagy is a physiological cellular process critical to maintaining cell homeostasis, which is involved in the lysosomal degradation of cytoplasmic organelles and macromolecules via the lysosomal pathway, suggesting that targeting autophagy is a potential therapeutic approach for cancer therapies. However, the underlying mechanism of autophagy in tRCC is still ambiguous. In this review, we summarize the autophagy-related signaling pathways associated with tRCC. Moreover, we examine the roles of autophagy and the immune response in tumorigenesis and investigate how these factors interact to facilitate or prevent tumorigenesis. Besides, we review the findings regarding the treatment of tRCC via induction or inhibition of autophagy. Hopefully, this study will shed some light on the functions and implications of autophagy and emphasize its role as a potential molecular target for therapeutic intervention in tRCC.

TRIM63 is a sensitive and specific biomarker for MiT family aberration-associated renal cell carcinoma

Microphthalmia-associated transcription factor (MiT) family aberration-associated renal cell carcinoma (MiTF-RCC) is a subtype of renal cell carcinoma harboring recurrent chromosomal rearrangements involving TFE3 or TFEB genes. MiTF-RCC is morphologically diverse, can histologically resemble common RCC subtypes like clear cell RCC and papillary RCC, and often poses a diagnostic challenge in genitourinary clinical and pathology practice. To characterize the MiTF-RCC at the molecular level and identify biomarker signatures associated with MiTF-RCC, we analyzed RNAseq data from MiTF-RCC, other RCC subtypes and benign kidney. Upon identifying TRIM63 as a cancer-specific biomarker in MiTF-RCC, we evaluated its expression independently by RNA in situ hybridization (RNA-ISH) in whole tissue sections from 177 RCC cases. We specifically included 31 cytogenetically confirmed MiTF-RCC cases and 70 RCC cases suspicious for MiTF-RCC in terms of clinical and morphological features, to evaluate and compare TRIM63 RNA-ISH results with the results from TFE3/TFEB fluorescence in situ hybridization (FISH), which is the current clinical standard. We confirmed that TRIM63 mRNA was highly expressed in all classes of MiTF-RCC compared to other renal tumor categories, where it was mostly absent to low. While the TRIM63 RNA-ISH and TFE3/TFEB FISH results were largely concordant, importantly, TRIM63 RNA-ISH was strongly positive in TFE3 FISH false-negative cases with RBM10-TFE3 inversion. In conclusion, TRIM63 can serve as a diagnostic marker to distinguish MiTF-RCC from other renal tumor subtypes with overlapping morphology. We suggest a combination of TFE3/TFEB FISH and TRIM63 RNA-ISH assays to improve the accuracy and efficiency of MiTF-RCC diagnosis. Accurate diagnosis of MiTF-RCC and other RCC subtypes would enable effective targeted therapy and avoid poor therapeutic response due to tumor misclassification.

NRF-1 directly regulates TFE3 and promotes the proliferation of renal cancer cells

The role of transcription factor binding to IGHM enhancer 3 (TFE3) in renal cell carcinoma (RCC) is not well understood. Nuclear respiratory factor 1 (NRF-1) may be the positive upstream regulatory gene of TFE3. The aim of the present study was to determine whether NRF-1 could directly regulate the expression of TFE3 and regulate tumorigenesis and progression of RCC through TFE3. Short hairpin RNA (shRNA) was used to silence the expression of NRF-1 in the 786-O human kidney adenocarcinoma cell line and the 293T human embryonic kidney cell line. Luciferase reporter assays were used to determine the relationship between NRF-1 and TFE3. The CHIP experiment was used to verify the actual binding of NRF-1 and TFE3 promoter regions. MitoTimer staining was used to measure mitochondrial biosynthesis. Flow cytometry was used to detect cell cycle and apoptosis. The 786-O and 293T cells were used to examine the underlying mechanism of action. The results demonstrated that NRF-1 could bind to the promoter region of the TFE3 gene and directly regulate the expression of TFE3. Following NRF-1 knockdown, the protein levels of phosphorylated (p)-AKT and p-S6 of mTOR pathway was inhibited, cell cycle progression was blocked, the levels of apoptosis increased, and mitochondrial generation was reduced. Following overexpression of TFE3, the levels of mTOR-associated markers were restored in NRF-1 knockdown cells. These findings suggest that NRF-1 may regulate the mTOR pathway through TFE3 and regulate the energy metabolism, proliferation and growth of cancer cells by directly regulating the expression of TFE3.

Key Renal Neoplasms With a Female Predominance

Renal neoplasms largely favor male patients; however, there is a growing list of tumors that are more frequently diagnosed in females. These tumors include metanephric adenoma, mixed epithelial and stromal tumor, juxtaglomerular cell tumor, mucinous tubular and spindle cell carcinoma, Xp11.2 (TFE3) translocation-associated renal cell carcinoma, and tuberous sclerosis complex (somatic or germline) associated renal neoplasms. The latter category is a heterogenous group with entities still being delineated. Eosinophilic solid and cystic renal cell carcinoma is the best-described entity, whereas, eosinophilic vacuolated tumor is a proposed entity, and the remaining tumors are currently grouped together under the umbrella of tuberous sclerosis complex/mammalian target of rapamycin-related renal neoplasms. The entities described in this review are often diagnostic considerations when evaluating renal mass tissue on biopsy or resection. For example, Xp11.2 translocation renal cell carcinoma is in the differential when a tumor has clear cell cytology and papillary architecture and occurs in a young or middle-aged patient. In contrast, tuberous sclerosis complex-related neoplasms often enter the differential for tumors with eosinophilic cytology. This review provides an overview of the clinical, gross, microscopic, immunohistochemical, genetic, and molecular alterations in key renal neoplasms occurring more commonly in females; differential diagnoses are also discussed regardless of sex predilection.

The Molecular Characteristics of Non-Clear Cell Renal Cell Carcinoma: What's the Story Morning Glory?

Non-clear cell renal cell carcinomas are a miscellaneous group of tumors that include different histological subtypes, each one characterized by peculiarity in terms of genetic alteration, clinical behavior, prognosis, and treatment response. Because of their low incidence and poor enrollment in clinical trials, alongside their heterogeneity, additional efforts are required to better unveil the pathogenetic mechanisms and, consequently, to improve the treatment algorithm. Nowadays, tyrosine kinase inhibitors, mTOR and MET inhibitors, and even cisplatin-based chemotherapy and immunotherapy are potential weapons that are still under evaluation in this setting. Various biomarkers have been evaluated for detecting progression and monitoring renal cell carcinoma, but more studies are necessary to improve this field. In this review, we provide an overview on the molecular characteristics of this group of tumors and the recently published trials, giving an insight into what might become the future therapeutic standard in this complex world of non-clear cell kidney cancers.

Uncommon Localization of Extrarenal Xp11.2 Translocation-associated Renal Cell Carcinoma (RCC): Case Report

The World Health Organization has recognized Xp11.2 translocation-associated renal cell carcinoma (RCC) as a distinct neoplasm that arises within the kidney. Although many reports of extrarenal carcinoma may be found in the literature, to the best of our knowledge, Xp11 translocation-associated RCC with intact kidneys has not been documented. This report describes a multilobulated right retroperitoneal soft tissue mass (7.9×5.3×12.6 cm) of a 37-year-old man complaining of abdominal pain in the right side. The patient underwent a computed tomography-guided biopsy. Microscopic evaluation reveals a tumor with papillary and sheaths architectures with cells revealing clear to eosinophilic cytoplasm. Immunohistochemical evaluation on the biopsy reveals that the tumor is positive for PAX-8, CD10, and TFE3. It is negative for CK7, EMA, Vimentin, RCC, CK8/18, D20, CD3, PLAP, OCT4, CD30, MART-1, Inhibin, S-100, HMB-45, Desmin, SMA, and DOG-1. The diagnosis was malignant epithelioid neoplasm and the diagnosis of translocation RCC was suggested. Excision was recommended. The patient underwent right radical nephrectomy with removal of this large mass. Pathologic examination showed a large cystic and solid, nonhomogenous mass with some necrotic areas, originating from the perirenal fat between the adrenal gland and the kidney. Microscopic features showed a tumor with papillary, rhabdoid, and clear cell features. Immunohistochemical stains showed that the tumor cells positively expressed AMACR, PAX-8, CD10, RCC, and TFE3, but were negative for cytokeratins, vimentin, HMB-45, desmin, SMA, EMA, and MSA. Cytogenetic studies confirmed the diagnosis of Xp11.2 translocation-associated RCC with positive TFE3 gene rearrangement. To the best of our knowledge, this type of extrarenal tumor has never been reported.

Folliculin: A Regulator of Transcription Through AMPK and mTOR Signaling Pathways

Folliculin (FLCN) is a tumor suppressor gene responsible for the inherited Birt-Hogg-Dubé (BHD) syndrome, which affects kidneys, skin and lungs. FLCN is a highly conserved protein that forms a complex with folliculin interacting proteins 1 and 2 (FNIP1/2). Although its sequence does not show homology to known functional domains, structural studies have determined a role of FLCN as a GTPase activating protein (GAP) for small GTPases such as Rag GTPases. FLCN GAP activity on the Rags is required for the recruitment of mTORC1 and the transcriptional factors TFEB and TFE3 on the lysosome, where mTORC1 phosphorylates and inactivates these factors. TFEB/TFE3 are master regulators of lysosomal biogenesis and function, and autophagy. By this mechanism, FLCN/FNIP complex participates in the control of metabolic processes. AMPK, a key regulator of catabolism, interacts with FLCN/FNIP complex. FLCN loss results in constitutive activation of AMPK, which suggests an additional mechanism by which FLCN/FNIP may control metabolism. AMPK regulates the expression and activity of the transcriptional cofactors PGC1α/β, implicated in the control of mitochondrial biogenesis and oxidative metabolism. In this review, we summarize our current knowledge of the interplay between mTORC1, FLCN/FNIP, and AMPK and their implications in the control of cellular homeostasis through the transcriptional activity of TFEB/TFE3 and PGC1α/β. Other pathways and cellular processes regulated by FLCN will be briefly discussed.

Napsin A Expression in Human Tumors and Normal Tissues

Background: Novel aspartic proteinase of the pepsin family A (Napsin A, TAO1/TAO2) is a functional aspartic proteinase which is involved in the maturation of prosurfactant protein B in type II pneumocytes and the lysosomal protein catabolism in renal cells. Napsin A is highly expressed in adenocarcinomas of the lung and is thus commonly used to affirm this diagnosis. However, studies have shown that other tumors can also express Napsin A.

Methods: To comprehensively determine Napsin A expression in normal and tumor tissue, 11,957 samples from 115 different tumor types and subtypes as well as 500 samples of 76 different normal tissue types were evaluable by immunohistochemistry on tissue microarrays.

Results: Napsin A expression was present in 16 different tumor types. Adenocarcinoma of the lung (85.6%), clear cell adenocarcinoma of the ovary (71.7%), clear cell adenocarcinoma of the endometrium (42.8%), papillary renal cell carcinoma (40.2%), clear cell (tubulo) papillary renal cell carcinoma (16.7%), endometrial serous carcinoma (9.3%), papillary thyroid carcinoma (9.3%) and clear cell renal cell carcinoma (8.2%) were among the tumors with the highest prevalence of Napsin A positivity. In papillary and clear cell renal cell carcinoma, reduced Napsin A expression was linked to adverse clinic-pathological features (p ≤ 0.03).

Conclusion: This methodical approach enabled us to identify a ranking order of tumors according to their relative prevalence of Napsin A expression. The data also show that loss of Napsin A is linked to tumor dedifferentiation in renal cell carcinomas.

Low expression of TRAF3IP2-AS1 promotes progression of NONO-TFE3 translocation renal cell carcinoma by stimulating N6-methyladenosine of PARP1 mRNA and downregulating PTEN

Background

NONO-TFE3 translocation renal cell carcinoma (NONO-TFE3 tRCC) is one subtype of RCCs associated with Xp11.2 translocation/TFE3 gene fusions RCC (Xp11.2 tRCCs). Long non-coding RNA (lncRNA) has attracted great attention in cancer research. The function and mechanisms of TRAF3IP2 antisense RNA 1 (TRAF3IP2-AS1), a natural antisense lncRNA, in NONO-TFE3 tRCC remain poorly understood.

Methods

FISH and qRT-PCR were undertaken to study the expression, localization and clinical significance of TRAF3IP2-AS1 in Xp11.2 tRCC tissues and cells. The functions of TRAF3IP2-AS1 in tRCC were investigated by proliferation analysis, EdU staining, colony and sphere formation assay, Transwell assay and apoptosis analysis. The regulatory mechanisms among TRAF3IP2-AS1, PARP1, PTEN and miR-200a-3p/153-3p/141-3p were investigated by luciferase assay, RNA immunoprecipitation, Western blot and immunohistochemistry.

Results

The expression of TRAF3IP2-AS1 was suppressed by NONO-TFE3 fusion in NONO-TFE3 tRCC tissues and cells. Overexpression of TRAF3IP2-AS1 inhibited the proliferation, migration and invasion of UOK109 cells which were derived from cancer tissue of patient with NONO-TFE3 tRCC. Mechanistic studies revealed that TRAF3IP2-AS1 accelerated the decay of PARP1 mRNA by direct binding and recruitment of N⁶-methyladenosie methyltransferase complex. Meanwhile, TRAF3IP2-AS1 competitively bound to miR-200a-3p/153-3p/141-3p and prevented those from decreasing the level of PTEN.

Conclusions

TRAF3IP2-AS1 functions as a tumor suppressor in NONO-TFE3 tRCC progression and may serve as a novel target for NONO-TFE3 tRCC therapy. TRAF3IP2-AS1 expression has the potential to serve as a novel diagnostic and prognostic biomarker for NONO-TFE3 tRCC detection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01059-5.

Histopathologic Characterization of Bladder Perivascular Epithelioid Cell Neoplasms (PEComa): A Series of 11 Cases With a Subset Having TFE3 Rearrangements

Perivascular epithelioid cell neoplasms (PEComas) of the bladder are extremely rare, with ~30 case reports. A subset of PEComas contain TFE3 gene rearrangement, however, the distinct histomorphologic features of these translocation tumors has not been fully explored in bladder PEComas. In our series, 11 cases of bladder PEComas were collected, including 1 internal and 10 consults, with 1 case previously reported. There was a female predominance (9 female, 2 male) with a mean age of 44.2 years (24 to 61 y). In only 1 of the 10 consult cases was PEComa considered in the differential diagnosis. In 10 of 11 cases, prominent epithelioid features were noted, with the final case having focal epithelioid morphology. Mitotic rate was increased in 2 of 11 cases, and 2 of 11 cases had cytological atypia. Two cases were malignant, with invasion into perivesicle tissue in 1 case, and metastases to lungs and brain followed by death in the other case. Immunohistochemically, there was strong, and diffuse staining for cathepsin K in 10/11 cases with the 1 negative case restained on a previously stained slide. HMB-45 was diffusely positive in 8/11 cases, while melan-A was present in only 1/10 cases. Muscle markers were variably expressed with positivity for both smooth muscle actin in 6/10 cases and desmin in 3/10 cases. Keratin AE1/3 was uniformly negative (0/11). In 5/8 cases where TFE3 was rearranged by fluorescence in situ hybridization, the morphology had a predominantly epithelioid, nested architecture. Overall, bladder PEComas are particularly difficult to diagnose given their rarity, are predominantly epithelioid and do not always express melanocytic markers. Diagnosis in the bladder requires a combination of morphologic characterization, exclusion of other diagnostic possibilities, positive Cathepsin K staining, variable melanocytic marker expression, with some cases showing a TFE3 gene rearrangement.

Diagnostic approach in TFE3-rearranged renal cell carcinoma: a multi-institutional international survey

Transcription factor E3-rearranged renal cell carcinoma (TFE3-RCC) has heterogenous morphologic and immunohistochemical (IHC) features.131 pathologists with genitourinary expertise were invited in an online survey containing 23 questions assessing their experience on TFE3-RCC diagnostic work-up.Fifty (38%) participants completed the survey. 46 of 50 participants reported multiple patterns, most commonly papillary pattern (almost always 9/46, 19.5%; frequently 29/46, 63%). Large epithelioid cells with abundant cytoplasm were the most encountered cytologic feature, with either clear (almost always 10/50, 20%; frequently 34/50, 68%) or eosinophilic (almost always 4/49, 8%; frequently 28/49, 57%) cytology. Strong (3+) or diffuse (>75% of tumour cells) nuclear TFE3 IHC expression was considered diagnostic by 13/46 (28%) and 12/47 (26%) participants, respectively. Main TFE3 IHC issues were the low specificity (16/42, 38%), unreliable staining performance (15/42, 36%) and background staining (12/42, 29%). Most preferred IHC assays other than TFE3, cathepsin K and pancytokeratin were melan A (44/50, 88%), HMB45 (43/50, 86%), carbonic anhydrase IX (41/50, 82%) and CK7 (32/50, 64%). Cut-off for positive TFE3 fluorescent in situ hybridisation (FISH) was preferably 10% (9/50, 18%), although significant variation in cut-off values was present. 23/48 (48%) participants required TFE3 FISH testing to confirm TFE3-RCC regardless of the histomorphologic and IHC assessment. 28/50 (56%) participants would request additional molecular studies other than FISH assay in selected cases, whereas 3/50 participants use additional molecular cases in all cases when TFE3-RCC is in the differential.Optimal diagnostic approach on TFE3-RCC is impacted by IHC and/or FISH assay preferences as well as their conflicting interpretation methods.

Stimulator of interferon genes (STING) immunohistochemical expression in the spectrum of perivascular epithelioid cell (PEC) lesions of the kidney

Angiomyolipoma is the prototype of renal perivascular epithelioid cell (PEC) lesions whose pathogenesis is determined by mutations affecting TSC genes, with eventual deregulation of the mTOR pathway. It is well known that mTOR complex protein is involved in autophagy, and recently the role of STING in this process has been demonstrated. Based on this background, we sought to investigate STING immunohistochemical expression in a series of PEC lesions of the kidney. Fifty classic angiomyolipomas, 14 epithelioid angiomyolipomas/pure epithelioid PEComas, two angiomyolipomas with epithelial cysts (AMLEC), and two intraglomerular PEC lesions were collected. Immunostaining for STING was carried out in all cases and FISH analysis using dual colour break apart TFE3 and TFEB probes was performed in all pure epithelioid PEComas and AMLEC. Control cases including 20 normal adult kidneys, five fetal kidneys, and 30 MiT family translocation renal cell carcinomas (the main differential diagnosis with epithelioid angiomyolipoma/pure epithelioid PEComa) were also immunohistochemically stained with STING. Strong and diffuse cytoplasmic expression of STING was observed in 100% of classic angiomyolipomas, AMLEC, and intraglomerular lesions, and in 79% (11/14) of epithelioid angiomyolipomas/pure epithelioid PEComas. TFE3 gene rearrangement was demonstrated in two epithelioid angiomyolipomas/pure epithelioid PEComas, both completely negative for STING. None of the MiT family translocation renal cell carcinomas expressed STING. In conclusion, we demonstrate the expression of STING in almost all PEC lesions of the kidney. This result provides novel insights into the possible role of autophagy in PEC lesions of the kidney. Moreover, this finding may be useful for diagnostic purposes, particularly in distinguishing epithelioid angiomyolipoma/pure epithelioid PEComa from MiT family translocation renal cell carcinoma and detecting intraglomerular PEC lesions.

Morphologic and Immunohistochemical Characteristics of Fluorescent In Situ Hybridization Confirmed TFE3-Gene Fusion Associated Renal Cell Carcinoma: A Single Institutional Cohort

TFE3-fusion associated renal cell carcinoma (TFE3-RCC) accounts for up to 5% adults and 40% of childhood RCC. Their comprehensive immunohistochemical (IHC) profile in correlation to fluorescence in situ hybridization (FISH) testing and their role in the diagnostic approach are not well documented because of lacking published data. FISH confirmed TFE3-RCC between years 2010 and 2020 were identified from institutional electronic database and retrospectively reviewed. Eighty-five TFE3-RCC were identified. Seventy-six of 85 (89.4%) TFE3-RCC cases had positive TFE3 expression, with diffuse and strong/moderate TFE3 expression in 45 (54.2%). Three (3.5%) TFE3-RCC had negative TFE3 expression whereas 6 (7%) cases had equivocal TFE3 expression. On the other hand, positive TFE3-IHC expression was observed in 17/29 (58.6%) TFE3-FISH negative RCC cases, although only 8 (27.5%) had diffuse and moderate/strong TFE3 expression. Diffuse and strong TFE3-IHC expression was statistically significant in predicting TFE3-FISH positivity (P<0.0001) regardless of morphologic features. After univariate and multivariate analyses, TFE3-IHC was the only parameter with significant predictive value for detecting positive TFE3-FISH (P<0.0001). On univariate analysis, sex, classic morphology, age, negative AE1/AE3 or cytokeratin 7 were not predictive of TFE3-FISH positivity. Diffuse and strong nuclear TFE3-IHC expression is significantly associated with TFE3-FISH positivity and can be used as a surrogate marker to confirm translocation associated cases. TFE3-rearranged RCCs show variable histomorphologic features and TFE3-FISH should be performed in cases presenting at a younger age or, regardless of the age, tumors with unusual morphology. Despite previous reports, negative pancytokeratin and positive cathepsin K expression may not be reliable markers for TFE3-RCC.

Pediatric and young adult renal cell carcinoma

Renal cell carcinoma (RCC) is rare in children but is the most common renal tumor in adults. Pediatric RCC has different clinical characteristics, histopathology, and treatment compared with adult disease. Databases were reviewed from inception to February 2020, identifying 32 publications pertaining to 350 patients under 27 years. Surgery is the cornerstone for cure in localized RCC. Lymph node dissection remains controversial. Conventional radiotherapy has no curative role in RCC; similarly, conventional chemotherapy has not proven to be effective in large cohorts. Pediatric metastatic RCC has a poor outlook. There are no published prospective studies demonstrating which adjuvant therapy could improve outcome. Sunitinib, a tyrosine kinase inhibitor, is recommended in this group despite limited evidence. This review provides an overview for pediatric RCC, including the evolving role of precision medicine.

Carbonic anhydrase IX (CA9) expression in multiple renal epithelial tumour subtypes

AIMS

Renal epithelial neoplasms (RENs) can be difficult to subclassify, owing to overlapping morphological features. Carbonic anhydrase 9 (CA9) is a common biomarker for clear cell renal cell carcinoma (CCRCC); however, the sensitivity and specificity across REN subtypes are less clear. The aim of this study was to investigate CA9 expression in RENs, especially those in the differential diagnosis with CCRCC and less common entities, to determine its reliability as a diagnostic biomarker.

METHODS AND RESULTS

CA9 immunostaining was performed on 262 RENs, including 119 CCRCCs and 143 non-CCRCC. Immunostaining was evaluated as negative (0%), rare (1+, 1-10%), focal (2+, 11-50%), or diffuse (3+, >50%). CCRCCs were 3+ CA9-positive in 93% of cases; 4% were CA9-negative. Sixty-seven percent of papillary renal cell carcinomas (RCCs) were 1+/2+ CA9-positive, whereas 33% were CA9-negative. Chromophobe RCCs were nearly always CA9-negative (93%), with 7% showing rare cell reactivity. Clear cell tubulopapillary RCCs (CCTPRCCs) were consistently 3+ CA9-positive, but with a cup-like staining pattern. Fifty-three percent of Xp11.2 RCCs were CA9-negative; however, 6% were 3+ CA9-positive and 12% were 2+ CA9-positive. Two of eight fumarate hydratase-deficient RCCs were 3+ CA9-positive. A small subset of the remaining RCCs showed rare to focal CA9 expression. All oncocytomas and eosinophilic solid and cystic RCCs were CA9-negative.

CONCLUSIONS

Overall, diffuse CA9 expression was identified in nearly all CCRCCs and in all CCTPRCCs (high sensitivity); however, CA9 was not entirely specific. At least focal CA9 expression can been seen in a subset of many RCCs, and such findings should be taken into consideration with other morphological, immunophenotypic and clinical findings.

Superficial malignant ossifying fibromyxoid tumors harboring the rare and recently described ZC3H7B-BCOR and PHF1-TFE3 fusions

Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm of uncertain differentiation and intermediate biologic potential. Up to 85% of OFMTs, including benign, atypical, and malignant forms, harbor fusion genes. Most commonly, the PHF1 gene localized to 6p21 is fused with EP400, but other fusion partners, such as MEAF6, EPC1, and JAZF1 have also been described. Herein, we present two rare cases of superficial OFMTs with ZC3H7B-BCOR and the very recently described PHF1-TFE3 fusions. The latter also exhibited moderate to strong diffuse immunoreactivity for TFE3. Reciprocally, this finding expands the entities with TFE3 rearrangements. Accumulation of additional data is necessary to determine if OFMTs harboring these rare fusions feature any reproducible clinicopathologic findings or carry prognostic and/or predictive implications.

Xp11 translocation renal cell carcinoma with morphological features mimicking multilocular cystic renal neoplasm of low malignant potential: a series of six cases with molecular analysis

AIMS

Xp11 translocation renal cell carcinoma (RCC) is a distinctive subtype of RCC with TFE3 (Transcription Factor Binding to IGHM Enhancer 3) gene rearrangement. The gross features in most Xp11 translocation RCCs closely resemble clear cell RCCs. In this study, we report six cases of Xp11 translocation RCCs with a unique multicystic architecture, reminiscent of multilocular cystic renal cell neoplasm of low malignant potential (MCRN-LMP).

METHODS AND RESULTS

Microscopically, the renal mass was well circumscribed with multilocular cystic architecture. The cyst walls and septa were mostly lined by a single layer of cells with clear cytoplasm and low-grade nuclei, reminiscent of MCRN-LMP. Psammoma bodies were detected in four cases. One particular patient was misdiagnosed with benign cysts in local hospitals and led to second operation. Tumour cells were settled according to the track of the first surgical procedure. TFE3 fluorescence in situ hybridization (FISH) assay confirmed the diagnosis of Xp11 translocation RCCs. FISH and RNA sequencing analyses confirmed MED15-TFE3 gene fusion in all six cases. Respective patients were alive, without any recent evidence of disease recurrence and/or metastasis.

CONCLUSIONS

Here, we introduce a relatively inertia-variant of Xp11 translocation RCC which mimics MCRN-LMP. The distinctive morphological condition is linked to MED15-TFE3 gene fusion. In fact, renal neoplasms with morphological features of MCRN-LMP, especially those containing psammoma bodies, should be routinely evaluated for evidence of TFE3 gene rearrangements.

Report From the International Society of Urological Pathology (ISUP) Consultation Conference on Molecular Pathology of Urogenital Cancers: III: Molecular Pathology of Kidney Cancer

Renal cell carcinoma (RCC) subtypes are increasingly being discerned via their molecular underpinnings. Frequently this can be correlated to histologic and immunohistochemical surrogates, such that only simple targeted molecular assays, or none at all, are needed for diagnostic confirmation. In clear cell RCC, VHL mutation and 3p loss are well known; however, other genes with emerging important roles include SETD2, BAP1, and PBRM1, among others. Papillary RCC type 2 is now known to include likely several different molecular entities, such as fumarate hydratase (FH) deficient RCC. In MIT family translocation RCC, an increasing number of gene fusions are now described. Some TFE3 fusion partners, such as NONO, GRIPAP1, RBMX, and RBM10 may show a deceptive fluorescence in situ hybridization result due to the proximity of the genes on the same chromosome. FH and succinate dehydrogenase deficient RCC have implications for patient counseling due to heritable syndromes and the aggressiveness of FH-deficient RCC. Immunohistochemistry is increasingly available and helpful for recognizing both. Emerging tumor types with strong evidence for distinct diagnostic entities include eosinophilic solid and cystic RCC and TFEB/VEGFA/6p21 amplified RCC. Other emerging entities that are less clearly understood include TCEB1 mutated RCC, RCC with ALK rearrangement, renal neoplasms with mutations of TSC2 or MTOR, and RCC with fibromuscular stroma. In metastatic RCC, the role of molecular studies is not entirely defined at present, although there may be an increasing role for genomic analysis related to specific therapy pathways, such as for tyrosine kinase or MTOR inhibitors.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

Renal Tumors of Childhood-A Histopathologic Pattern-Based Diagnostic Approach

Renal tumors comprise approximately 7% of all malignant pediatric tumors. This is a highly heterogeneous group of tumors, each with its own therapeutic management, outcome, and association with germline predispositions. Histopathology is the key in establishing the correct diagnosis, and therefore pathologists with expertise in pediatric oncology are needed for dealing with these rare tumors. While each tumor shows different histologic features, they do have considerable overlap in cell type and histologic pattern, making the diagnosis difficult to establish, if based on routine histology alone. To this end, ancillary techniques, such as immunohistochemistry and molecular analysis, can be of great importance for the correct diagnosis, resulting in appropriate treatment. To use ancillary techniques cost-effectively, we propose a pattern-based approach and provide recommendations to aid in deciding which panel of antibodies, supplemented by molecular characterization of a subset of genes, are required.

[MiT family translocation renal cell carcinomas: Natural history, molecular features and multidisciplinary management]

MiT family translocation renal cell carcinomas (tRCC) represent a rare subtype of renal cell carcinomas. These tumors have been introduced for the first time in the World Health Classification (WHO) classification of kidney cancers in 2004. tRCC are characterized by reccurent translocations involving members of the MiT family transcription factors, mainly TFE3 and TFEB. The estimated incidence of these tumors is ∼1-5 % among all renal cell carcinomas, with female prodominance. tRCC were initially described in children, and the spectrum has been expanded over time to encompass adolescents and adults. TFE3- and TFEB-rearranged RCC harbor characteristic clinicopathological and immunohistochemical features and fluorescent hybridization in situ is considered the gold standard for their diagnosis, although it has some limitations especially when the partners are located in the vicinity of TFE3. Nephron-sparing surgery is an efficient treatment of localized cases when achievable. In metastatic setting, targeted agents and immunotherapy showed modest efficacy, with response rates and median overall survival inferior to those observed in clear-cell renal cell carcinomas. Management of tRCC necessite a multidisciplinary team and accrual in clinical trials have to be encouraged when possible. Novel biological insights are urgently awaited to better understand the mechanisms associated with kidney oncogenesis in this setting, and ultimately help to identify therapeutic targets.

Clinicopathological Findings on 28 Cases with XP11.2 Renal Cell Carcinoma

Xp11.2 translocation carcinoma is a distinct subtype of renal cell carcinoma characterized by translocations involving the TFE3 gene. Our study included the morphological, immunohistochemical and clinicopathological examination of 28 Xp11.2 RCCs. The immunophenotype has been assessed by using CA9, CK7, CD10, AMACR, MelanA, HMB45, Cathepsin K and TFE3 immunostainings. The diagnosis was confirmed by TFE3 break-apart FISH in 25 cases. The ages of 13 male and 15 female patients, without underlying renal disease or having undergone chemotherapy ranged from 8 to 72. The mean size of the tumors was 78.5 mm. Forty-three percent of patients were diagnosed in the pT3/pT4 stage with distant metastasis in 6 cases. Histological appearance was branching-papillary composed of clear cells with voluminous cytoplasm in 13 and variable in 15 cases, including one tumor with anaplastic carcinoma and another with rhabdoid morphology. Three tumors were labeled with CA9, while CK7 was negative in all cases. Diffuse CD10 reaction was observed in 17 tumors and diffuse AMACR positivity was described in 14 tumors. The expression of melanocytic markers and Cathepsin K were seen only in 7 and 6 cases, respectively. TFE3 immunohistochemistry displayed a positive reaction in 26/28 samples. TFE3 rearrangement was detected in all the analyzed cases (25/25), including one with the loss of the entire labeled break-point region. The follow-up time ranged from 2 to 300 months, with 7 cancer-related deaths. In summary, Xp11.2 carcinoma is an uncommon form of renal cell carcinoma with a variable histomorphology and rather aggressive clinical course.

Gene fusion analysis in renal cell carcinoma by FusionPlex RNA-sequencing and correlations of molecular findings with clinicopathological features

Translocation renal cell carcinoma (tRCC) affects younger patients and often presents as advanced disease. Accurate diagnosis is required to guide clinical management. Here we evaluate the RNA-sequencing FusionPlex platform with a 115-gene panel including TFE3 and TFEB for tRCC diagnosis and correlate molecular findings with clinicopathological features. We reviewed 996 consecutive RCC cases from our institution over the preceding 7 years and retrieved 17 cases with histological and immunohistochemical features highly suggestive of either TFE3 (n = 16) or TFEB (n = 1). Moderate to strong labeling for TFE3 was present in 15 cases; two cases with weak TFE3 expression were melan-A or cathepsin-K positive. RNA-sequencing detected gene rearrangements in eight cases: PRCC-TFE3 (3), ASPSCR1-TFE3 (2), LUC7L3-TFE3 (1), SFPQ-TFE3 (1), and a novel SETD1B-TFE3 (1). FISH assays of 11 tumors verified six positive cases concordant with FusionPlex analysis results. Two other cases were confirmed by RT-PCR. FusionPlex was superior to FISH by providing precise breakpoints for tRCC-related genes in a single assay and allowing identification of both known and novel fusion partners, thereby facilitating clinicopathological correlations as fusion partners can influence tumor appearance, immunophenotype, and behavior. Cases with partner genes PRCC and novel partner SETD1B were associated with prominent papillary architecture while cases with partner genes ASPSCR1 and LUC7L3 were associated with a predominantly nested/alveolar pattern. The case with SFPQ-TFE3 fusion was characterized by biphasic morphology mimicking TFEB-like translocation RCC. We recommend FusionPlex analysis of RCC in patients under age 50 or when the histologic appearance suggests tRCC.

Molecular Genetics of Renal Cell Tumors: A Practical Diagnostic Approach

Renal epithelial cell tumors are composed of a heterogeneous group of tumors with variable morphologic, immunohistochemical, and molecular features. A "histo-molecular" approach is now an integral part of defining renal tumors, aiming to be clinically and therapeutically pertinent. Most renal epithelial tumors including the new and emerging entities have distinct molecular and genetic features which can be detected using various methods. Most renal epithelial tumors can be diagnosed easily based on pure histologic findings with or without immunohistochemical examination. Furthermore, molecular-genetic testing can be utilized to assist in arriving at an accurate diagnosis. In this review, we presented the most current knowledge concerning molecular-genetic aspects of renal epithelial neoplasms, which potentially can be used in daily diagnostic practice.

Primary Thyroid Gland Alveolar Soft Part Sarcoma

Alveolar soft part sarcoma (ASPS) is a rare soft tissue tumor of unknown histogenesis generally characterized by the der(17)t(X;17)(p11.2;q25) translocation which results in the ASPSCR1-TFE3 gene fusion. Primary ASPS of the thyroid gland has not yet been reported. During oncology follow-up for breast cancer, a pulmonary nodule and thyroid gland mass were identified in a 71-year-old Korean male. Thyroid ultrasound showed a 5.7 cm left thyroid gland mass. After several fine needle aspirations, a thyroid gland lobectomy was performed after documenting only non-caseating granulomatous inflammation in a biopsy of the lung nodule. A 7.6 cm bulging nodular thyroid gland mass was identified, showing significant destructive invasion. Alveolar nests of large polygonal, eosinophilic, granular neoplastic cells were separated by vascularized stroma. Colloid was absent. Tumor necrosis and increased mitoses were identified. The neoplastic cells were positive with TFE3 and CD68, but negative with pancytokeratin, thyroglobulin, TTF-1, napsin-A, calcitonin, PAX8, CAIX, S100 protein, HMB45, SMA, and desmin. FISH confirmed a TFE3 gene rearrangement. The differential includes several primary thyroid gland epithelial neoplasms, paraganglioma, PEComa, melanoma, crystal storage disease, and metastatic carcinomas, especially Xp11 translocation renal cell carcinoma. The patient has refused additional therapy, but is alive without tumor identified (primary or metastatic).

Xp11 translocation renal cell carcinoma and clear cell renal cell carcinoma with TFE3 strong positive immunostaining: morphology, immunohistochemistry, and FISH analysis

TFE3 is accepted as a good marker for the diagnosis of Xp11 translocation renal cell carcinoma. However, the significance of TFE3 in other types of renal cell carcinomas remains unclear. We examined the expression of TFE3 using immunohistochemistry by automated Ventana BenchMark XT system in 1818 consecutive renal cell carcinomas and verified the strong positive cases with TFE3 break-apart fluorescence in situ hybridization and RNA sequencing. Among the 27 renal cell carcinomas with TFE3 strong positive immunostaining, 20 cases were diagnosed as Xp11 translocation renal cell carcinoma, and seven cases were diagnosed as clear cell renal cell carcinoma. We further analyzed the morphology, clinicopathological features, and immunohistochemistry markers (CK7, CD117, CD10, P504s, vimentin, CA-IX, AE1/AE3, EMA, HMB45, Melan-A, and cathepsin K) of them. Pale to eosinophilic flocculent cytoplasm and psammomatous calcification were seen only in Xp11 translocation renal cell carcinomas (P < 0.05). Tumor necrosis occurred in all four cases of Xp11 translocation renal cell carcinomas with pT3a stage, which had local recurrence and distant metastasis (two of them died) within 3 years. The expressions of Vimentin, CA-IX, AE1/AE3, and EMA were significantly different between them (P < 0.05). CA-IX was diffusely strong positive in clear cell renal cell carcinomas but negative or focally mild positive in Xp11 translocation renal cell carcinomas. Our study first demonstrates that a very small minority (0.4%) of clear cell renal cell carcinomas with TFE3 strong positive immunostaining, which points out a potential pitfall in diagnosis of Xp11 translocation renal cell carcinomas by TFE3 immunohistochemistry. CA-IX is a good marker to distinguish clear cell renal cell carcinoma with TFE3 strong positive immunostaining from Xp11 translocation renal cell carcinoma. Tumor necrosis could be a potential factor relevant to pT3a stage, which may be a high-risk factor for the patients with Xp11 translocation renal cell carcinomas.