Renal Cell Carcinomas With t(6;11)(p21;q12): A Clinicopathologic Study Emphasizing Unusual Morphology, Novel Alpha-TFEB Gene Fusion Point, Immunobiomarkers, and Ultrastructural Features, As Well As Detection of the Gene Fusion by Fluorescence In Situ Hybridization

Paediatric renal tumours: an update on challenges and recent developments

Paediatric renal tumours include a broad range of neoplasms which largely differ, but also overlap to a smaller extent, with adult kidney cancer. These include the embryonal tumour nephroblastoma, which accounts for the majority of cases of kidney cancer in the first decade of life and, despite boasting a cure in ~ 90% cases, still presents clinical challenges in a small proportion of cases. A variety of less common mesenchymal tumours, including the mostly indolent congenital mesoblastic nephroma, clear cell sarcoma of kidney which continues to be associated with poor outcomes for higher stage disease, and the typically lethal malignant rhabdoid tumour, form the bulk of the remaining presentations in the first decade. All three of these represent the intrarenal form of a wider 'family' of genetically related and histologically overlapping entities occurring in soft tissue and other anatomical locations. The latter two are examples of aggressive 'epigenetic' tumours driven by dysregulation of chromatin. In the second decade of life, renal cell carcinoma dominates, and with molecular characterisation many distinct subtypes are now described. Herein we discuss the developments in relation to diagnostic categorisation of paediatric renal cancers and how deeper understanding of the underlying biology is already providing therapeutic opportunity, while also focussing on the challenges that remain for the pathologist.

Incidental Detection of TFEB-Amplified Renal Cell Carcinoma by Colocated Gene Amplification of CCND3 (6p21): A Case Report and Review of the Literature

TFEB-amplified renal cell carcinoma (RCC), which belongs to the MITF family of RCC, is characterized by genomic amplification at the 6p21.1 locus where the TFEB gene is located. The vascular endothelial growth factor A and cyclin D3 genes are also located at this same locus. When tumors lack classic morphologic features, they may be classified as "RCC not otherwise specified (NOS)." However, it is increasingly important to accurately diagnose the RCC subtype to define the patient's individual prognosis and select the subsequent therapeutic modalities, which now include targeted agents. Therefore, knowledge of the diagnostic features of TFEB-altered RCCs, such as t(6;11) RCCs and TFEB-amplified RCCs, is critical for identifying these tumors. Herein, we present an interesting case of TFEB-amplified RCC that was initially diagnosed as RCC NOS on biopsy of a renal tumor in a community practice setting with available molecular findings demonstrating CCND3 amplification. The genetic abnormality was "accidentally" detected due to the amplification of the colocated CCND3 gene at the 6p21 locus of the TFEB gene on a limited genetic sequencing panel. This case highlights the importance of molecular tests in accurately diagnosing RCC and carefully interpreting molecular findings in the context of histomorphologic features.

Loss of YAP1 C-terminus expression as an ancillary marker for metaplastic thymoma: a potential pitfall in detecting YAP1::MAML2 gene rearrangement

AIMS

Metaplastic thymoma is a rare thymic tumour characterized by Yes Associated Protein 1 (YAP1) and Mastermind Like Transcriptional Coactivator 2 (MAML2) gene fusions resulting from an intrachromosomal inversion of chromosome 11. Immunohistochemistry with an antibody directed against the C-terminus of YAP1 has shown loss of expression in YAP1-rearranged vascular neoplasms, poromas, and porocarcinomas. This study aimed to validate an anti-YAP1 C-terminal antibody as an ancillary immunohistochemical marker for the diagnosis of metaplastic thymoma.

MATERIALS AND METHODS

Ten metaplastic thymomas were selected for the current study. Fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and reverse transcription-polymerase chain reaction (RT-PCR) analyses were performed to detect YAP1::MAML2 fusions. We then performed immunohistochemistry to detect YAP1 C-terminus expression in 10 metaplastic thymomas, 50 conventional thymomas (10 each of type A thymoma, type AB thymoma, type B1 thymoma, type B2 thymoma, and type B3 thymoma) and seven thymic carcinomas.

RESULTS

All 10 cases showed narrow split signals with a distance of nearly two signal diameters and sometimes had false-negative results in YAP1 and MAML2 break-apart FISH (BA-FISH). Abnormal colocalized signals of the YAP1::MAML2 fusion were observed in all 10 cases using fusion FISH (F-FISH) assays. Eight of 10 cases with adequate nucleic acids were successfully sequenced and all showed YAP1::MAML2 fusions; in two cases the fusions were detected by both DNA and RNA sequencing and in six cases by RNA sequencing only. YAP1::MAML2 fusion transcripts were identified in four cases by RT-PCR. Metaplastic thymoma showed loss of YAP1 C-terminus expression in all 10 (100%) cases. All other thymic neoplasms showed retained YAP1 C-terminus expression.

CONCLUSION

YAP1 C-terminus immunohistochemistry is a highly sensitive and specific ancillary marker that distinguishes metaplastic thymoma from its mimics. BA-FISH assays could not effectively detect YAP1::MAML2 fusions due to the proximity of the two genes. Loss of YAP1 C-terminus expression is a reliable surrogate for the detection of YAP1::MAML2 fusions in metaplastic thymoma.

TFEB-associated renal cell carcinoma: A case report and literature review

RATIONALE

TFEB-associated renal cell carcinoma is very rare and belongs to the microphthalmia - associated transcription family translocation renal cell carcinoma.

PATIENT CONCERNS

Hospitalized for fever, a 29-year-old male patient had a left kidney lesion without any additional discomfort.

DIAGNOSES

Histopathological and immunohistochemical results were corresponding with TFEB renall cell carcinoma features.

INTERVENTIONS

Surgical resection of the tumor was performed.

OUTCOMES

After 8 months of follow-up, no tumor recurrence was observed.

LESSONS

TFEB-associated renal cell carcinoma is rare. The diagnosis is explicit. However, the optimal treatment needs to be further explored.

Proteogenomic characterization of MiT family translocation renal cell carcinoma

Microphthalmia transcription factor (MiT) family translocation renal cell carcinoma (tRCC) is a rare type of kidney cancer, which is not well characterized. Here we show the comprehensive proteogenomic analysis of tRCC tumors and normal adjacent tissues to elucidate the molecular landscape of this disease. Our study reveals that defective DNA repair plays an important role in tRCC carcinogenesis and progression. Metabolic processes are markedly dysregulated at both the mRNA and protein levels. Proteomic and phosphoproteome data identify mTOR signaling pathway as a potential therapeutic target. Moreover, molecular subtyping and immune infiltration analysis characterize the inter-tumoral heterogeneity of tRCC. Multi-omic integration reveals the dysregulation of cellular processes affected by genomic alterations, including oxidative phosphorylation, autophagy, transcription factor activity, and proteasome function. This study represents a comprehensive proteogenomic analysis of tRCC, providing valuable insights into its biological mechanisms, disease diagnosis, and prognostication.

Research Hotspots and Trends Analysis of TFEB: A Bibliometric and Scientometric Analysis

Objective

To explore the development context, research hotspots and frontiers of Transcription factor EB (TFEB) from 1991 to 2021 by bibliometric analysis.

Methods

Publications about TFEB research from 1991 to 2021 were retrieved from the Web of Science Core Collection (WoSCC). Excel 2007 was used to collect basic information, including publications, research areas. VOSviewer 1.6.17 was used to analyze co-authorship of countries, institutes and authors. Co-citation of cited authors, cited references were analyzed by CiteSpace V.5.8.R3. In addition, CiteSpace was used to analyze keywords cluster and forecast research frontiers.

Results

A total of 1,059 literatures were retrieved, including 1,340 research institutes and 393 academic journals. The main area of research related to TFEB is biology (340), the most published country and institutes were the United States (487) and Baylor College of Medicine (70). Settembre C owned the highest co-citations (663). Trending keywords may indicate frontier topics, including “Alzheimer’s disease,” “Parkinson’s disease,” “(p21; q12),” “melanoma,” “pancreatic cancer,” “breast cancer,” “calcineurin,” “TFE3,” “trehalose,” and “curcumin.”

Conclusion

This research provides valuable information for the study of TFEB. Disease research focuses more on neurodegenerative diseases (NDs) and tumors. Trehalose and curcumin are novel agents acting on TFEB. Rap-TRPML1-Calcineurin-TFEB and TFE3 are increasing signal pathway researches, similarly, the molecular biological mechanism of TFEB needs further exploration.

Nuclear translocation of ASPL-TFE3 fusion protein creates favorable metabolism by mediating autophagy in translocation renal cell carcinoma

The ASPL-TFE3 fusion gene, resulting from t(X;17)(p11.2;q25.3), is one of the most commonly identified fusion genes in Xp11 translocation renal cell carcinoma (tRCC). However, its roles and underlying mechanism in RCC development are not yet clear. Here, we identified ASPL-TFE3 fusion as the most common tRCC subtype in a Chinese population (29/126, 23.03%). This fusion protein translocated into the nucleus and promoted RCC cell proliferation both in vitro and in vivo. Mechanistically, the fusion protein transcriptionally activated the lysosome-autophagy pathway by binding to the promoters of lysosome-related genes. Autophagy, activated by ASPL-TFE3, enabled RCC cells to escape energy stress by promoting the utilization of proteins and lipids. Moreover, we found that the ASPL-TFE3 fusion escaped regulation by the classic mTOR-TFE3 signal and instead activated phospho-mTOR and its downstream targets. Finally, targeting both autophagy and the mTOR axis resulted in a greater antiproliferative effect than single pathway inhibition. In summary, these results confirmed the ASPL-TFE3 fusion as a master regulator of metabolic adaptation mediated by autophagy in tRCC. The simultaneous manipulation of autophagy and the mTOR axis may represent a novel treatment strategy for ASPL-TFE3 fusion RCC.

Molecular Heterogeneity of Xp11.2 Translocation Renal Cell Carcinoma: The Correlation Between Split Signal Pattern in FISH and Prognosis

PURPOSE

Xp11.2 translocation renal cell carcinoma (Xp11.2 tRCC) is a distinct subtype of renal cell carcinoma (RCC) characterized by chromosomal translocations involving TFE3 gene. TFE3 break-apart fluorescence in situ hybridization (FISH) assay is an effective tool to diagnose Xp11.2 tRCC. The aim of this study is to evaluate the correlation between split signal pattern in FISH and the clinicopathological characteristics of Xp11.2 tRCC.

PATIENTS AND METHODS

We reviewed 2037 RCC patients who underwent partial nephrectomy or radical nephrectomy from January 2007 to March 2020 in our institution. Forty-nine cases were diagnosed as Xp11.2 tRCC and their split signal patterns were evaluated. X-tile software was used to determine the optimal cut-off value of the percentage of split signal in FISH. Kaplan-Meier analysis and Cox regression analysis were performed to assess the relationship between signal pattern of FISH and the prognosis.

RESULTS

Among the 49 patients, 13 patients and 36 patients were classified into high and low split signal group, respectively. Nine cases showed extra amplification signal pattern and 40 cases showed typical translocation signal pattern. Multivariate analysis demonstrated that high percentage of split signal and amplification signal pattern were the independent predictors for progression-free survival (PFS) whereas only pT stage was associated independently with overall survival (OS).

CONCLUSION

Xp11.2 tRCC cases with high percentage of split signals or amplification signal pattern may have a worse outcome, and the two indicators need to be highlighted in clinical practice.

Contribution of TFEB-mediated autophagy to tubulointerstitial fibrosis in mice with adenine-induced chronic kidney disease

Autophagy has been implicated in the pathogenesis of chronic kidney disease (CKD). Transcription factor EB (TFEB) is a master controller of autophagy. However, the pathophysiological roles of TFEB in modulating autophagy and tubulointerstitial injury in CKD are unknown. This study aimed to determine whether TFEB-mediated autophagy contributed to the tubulointerstitial injury in mice with CKD. After the mice were treated with an adenine diet (0.2 % adenine) for 8 weeks, the development of CKD was observed to be characterised by increased levels of plasma blood urea nitrogen (BUN), creatinine (Cre), tubulointerstitial inflammation and fibrosis. Immunohistochemical and Western blot analysis further revealed that TFEB and autophagy genes were significantly up-regulated in the kidney of the mice with adenine-induced CKD, and this increase was mostly found in the tubular epithelial cells. Interestingly, a similar expression pattern of TFEB-autophagy genes was observed in tubular epithelial cells in the kidney tissue of patients with immunoglobulin A (IgA) nephropathy. Moreover, a pathogenic role of TFEB in adenine-induced CKD was speculated because the pharmacological activation of TFEB by trehalose failed to protect mice from tubulointerstitial injuries. In the epithelioid clone of normal rat kidney cells (NRK-52E), the activation of TFEB by trehalose increased autophagy induction, cell death and inflammatory cytokine (Interleukin-6, IL-6) release. Collectively, these results suggested that the activation of TFEB-mediated autophagy might cause autophagic cell death and inflammation in tubular epithelial cells, contributing to renal fibrosis in adenine-induced CKD. This study provided novel insights into the pathogenic role of TFEB in CKD associated with a high purine diet.

Pediatric Renal Tumors: Updates in the Molecular Era

Molecular characterization has led to advances in the understanding of pediatric renal tumors, including the association of pediatric cystic nephromas with DICER1 tumor syndrome, the metanephric family of tumors with somatic BRAF mutations, the characterization of ETV6-NTRK3-negative congenital mesoblastic nephromas, the expanded spectrum of gene fusions in translocation renal cell carcinoma, the relationship of clear cell sarcoma of the kidney with other BCOR-altered tumors, and the pathways affected by SMARCB1 alterations in rhabdoid tumors of the kidney. These advances have implications for diagnosis, classification, and treatment of pediatric renal tumors.

A Tale of 2 Morphologies: Diagnostic Pitfalls in TFEB-Associated Renal Cell Carcinomas, Including a Novel NEAT1-TFEB Fusion

AIMS

Translocation-associated renal cell carcinomas (RCCs) have been extensively subcharacterized in recent years, such that each is largely recognized by the 2016 World Health Organization as categorical neoplastic entities in the genitourinary tract. Those belonging to the t(6;11) family of tumors classically have a fusion between TFEB and MALAT1/α, and display a particular histomorphology. Specifically, they show a biphasic population of both small and large epithelioid cells, the smaller component of which surrounds basement membrane-type material. Despite this apt description, the tumors have variable morphology and mimic other RCCs including those with TFE3 translocations. Therefore, a high degree of suspicion is required to make the correct diagnosis.

METHODS

The 2 cases described in this article were of strikingly different appearance, and initially considered consistent with other non-translocation-associated renal tumors. These included clear cell RCC (CCRCC), perivascular epithelioid cell tumor (PEComa), and other eosinophilic RCCs (mainly papillary RCC type 2).

RESULTS

Using RNA sequencing techniques, they were found to harbor distinct pathogenic rearrangements involving the TFEB gene, namely, fusions with CLTC and NEAT1 (the latter partnering heretofore never reported).

CONCLUSIONS

These alterations manifested in 2 notably dissimilar lesions, underscoring the importance of including this family of carcinomas in the differential of any renal neoplasm that does not display immunophenotypic characteristics consistent with its morphology.

Juxtaglomerular cell tumor: Clinicopathologic evaluation in a large series emphasizing its broad histologic spectrum

The juxtaglomerular cell tumor (JCT) is a rare renal tumor. We re-evaluated the clinicopathologic features of 21 JCTs to summarize their variable morphologies. Immunohistochemical, fluorescent in situ hybridization and periodic acid-Schiff stains were routinely performed, and four JCT cases were detected via transmission electron microscopy. The 21 JCTs involved five males and 16 females, ranging in age from 19 years to 69 years (mean, 36.9 years; median, 34 years). The tumors were composed of large, small, or spindle cells with a round, oval or polygonal shape, arranged in various growth patterns. Both necrosis (1/21) and mitosis (2/21, with 1/50HFP, 8/50HFP) was rarely appreciated. All cases were immunoreactive for renin and CD34 (21/21), and few were positive for α-SMA (13/21;11/21, focally; 2/21, diffusely,), CD117 (9/21, focally) and synaptophysin (3/21, focally). Ultrastructurally, all four cases exhibited secretory granules in varying sizes in the cytoplasm, two of which exhibited cellular junctions. Almost all cases (20/21) had a favorable prognosis, but one succumbed due to bone and hepatic metastases, which corresponds to malignant JCT. Our study demonstrates that JCTs may have atypical clinical presentations and variable histologic appearances. A familiarity with these features may contribute to a correct diagnosis.

Clinicopathologic and Molecular Analysis of the TFEB Fusion Variant Reveals New Members of TFEB Translocation Renal Cell Carcinomas (RCCs): Expanding the Genomic Spectrum

Xp11 renal cell carcinoma (RCC) with different gene fusions may have different clinicopathologic features. We sought to identify variant fusions in TFEB translocation RCC. A total of 31 cases of TFEB RCCs were selected for the current study; MALAT1-TFEB fusion was identified in 25 cases (81%, 25/31) using fusion probes. The remaining 6 cases (19%, 6/31) were further analyzed by RNA sequencing and 5 of them were detected with TFEB-associated gene fusions, including 2 ACTB-TFEB, 1 EWSR1-TFEB, 1 CLTC-TFEB, and 1 potential PPP1R10-TFEB (a paracentric inversion of the TFEB gene, consistent with "negative" TFEB split FISH result, and advising a potential diagnostic pitfall in detecting TFEB gene rearrangement). Four of the 5 fusion transcripts were successfully validated by reverse transcription-polymerase chain reaction and Sanger sequencing. Morphologically, approximately one third (29%, 9/31) of TFEB RCCs showed typical biphasic morphology. The remaining two thirds of the cases (71%, 22/31) exhibited nonspecific morphology, with nested, sheet-like, or papillary architecture, resembling other types of renal neoplasms, such as clear cell RCC, Xp11 RCC, perivascular epithelioid cell tumor (PEComa), or papillary RCC. Although cases bearing a MALAT1-TFEB fusion demonstrated variable morphologies, all 9 cases featuring typical biphasic morphology were associated with MALAT1-TFEB genotype. Accordingly, typical biphasic morphology suggests MALAT1-TFEB fusion, whereas atypical morphology did not suggest the specific type of fusion. Isolated or clustered eosinophilic cells were a common feature in TFEB RCCs, which may be a useful morphology diagnostic clue for TFEB RCCs. Clinicopathologic variables assessment showed that necrosis was the only morphologic feature that correlated with the aggressive behavior of TFEB RCC (P=0.004). In summary, our study expands the genomic spectrum and the clinicopathologic features of TFEB RCCs, and highlights the challenges of diagnosis and the importance of subtyping of this tumor by combining morphology and multiple molecular techniques.

TFEB Expression Profiling in Renal Cell Carcinomas: Clinicopathologic Correlations

TFEB is overexpressed in TFEB-rearranged renal cell carcinomas as well as in renal tumors with amplifications of TFEB at 6p21.1. As recent literature suggests that renal tumors with 6p21.1 amplification behave more aggressively than those with rearrangements of TFEB, we compared relative TFEB gene expression in these tumors. This study included 37 TFEB-altered tumors: 15 6p21.1-amplified and 22 TFEB-rearranged (including 5 cases from The Cancer Genome Atlas data set). TFEB status was verified using a combination of fluorescent in situ hybridization (n=27) or comprehensive molecular profiling (n=13) and digital droplet polymerase chain reaction was used to quantify TFEB mRNA expression in 6p21.1-amplified (n=9) and TFEB-rearranged renal tumors (n=19). These results were correlated with TFEB immunohistochemistry. TFEB-altered tumors had higher TFEB expression when normalized to B2M (mean: 168.9%, n=28), compared with non-TFEB-altered controls (mean: 7%, n=18, P=0.005). Interestingly, TFEB expression in tumors with rearrangements (mean: 224.7%, n=19) was higher compared with 6p21.1-amplified tumors (mean: 51.2%, n=9; P=0.06). Of note, classic biphasic morphology was only seen in TFEB-rearranged tumors and when present correlated with 6.8-fold higher TFEB expression (P=0.00004). Our results suggest that 6p21.1 amplified renal tumors show increased TFEB gene expression but not as much as t(6;11) renal tumors. These findings correlate with the less consistent/diffuse expression of downstream markers of TFEB activation (cathepsin K, melan A, HMB45) seen in the amplified neoplasms. This suggests that the aggressive biological behavior of 6p21.1 amplified renal tumors might be secondary to other genes at the 6p21.1 locus that are co-amplified, such as VEGFA and CCND3, or other genetic alterations.

The role of TFEB in tumor cell autophagy: Diagnostic and therapeutic opportunities

Autophagy is a conserved "self-eating" recycling process which removes aggregated or misfolded proteins, or defective organelles, to maintain cellular hemostasis. In the autophagy-lysosome pathway (ALP), clearance of unwanted debris and materials occurs through the generation of the autophagosome, a complex of double-membrane bounded vesicles that form around cytosolic cargos and catabolize their contents by fusion to lysosomes. In tumors, autophagy has dichotomous functions via preventing tumor initiation but promoting tumor progression. The basic helix-loop-helix leucine zipper transcription factor EB (TFEB) activates the promoters of genes encoding for proteins, which participate in this cellular degradative system by regulating lysosomal biogenesis, lysosomal acidification, lysosomal exocytosis and autophagy. In humans, disturbances of ALP are related to various pathological conditions. Recently, TFEB dysregulation was found to have a crucial pathogenic role in different tumors by modulating tumor cell autophagy. Notably, in renal cell carcinomas, different TFEB gene fusions were reported to promote oncogenic features. In this review, we discuss the role of TFEB in human cancers with a special focus on potential diagnostic and therapeutic implications.

Five decades of urologic pathology: the accelerating expansion of knowledge in renal cell neoplasia

Those who are knowledgeable in cosmology inform us that the expansion of the universe is such that the velocity at which a distant galaxy is receding from the observer is continually increasing with time. We humbly paraphrase that as "The bigger the universe gets, the faster it gets bigger." This is an interesting analogy for the expansion of knowledge in the field of renal tumor pathology over the past 30 to 50 years. It is clear that a multitude of dedicated investigators have devoted incalculable amounts of time and effort to the pursuit of knowledge about renal epithelial neoplasms. As a consequence of the contributions of numerous investigators over many decades, the most recent World Health Organization classification of renal neoplasms includes about 50 well defined and distinctive renal tumors, as well as various miscellaneous and metastatic tumors. In addition, a number of emerging or provisional new entities are under active investigation and may be included in future classifications. In this review, we will focus on a number of these tumors, tracing as accurately as we can the origins of their discovery, relating relevant additions to the overall knowledge base surrounding them, and in some instances addressing changes in nomenclature.

"Atrophic Kidney"-like Lesion: Clinicopathologic Series of 8 Cases Supporting a Benign Entity Distinct From Thyroid-like Follicular Carcinoma

Renal mass lesions with a follicular architecture resembling atrophic kidney have been described, but their distinction from thyroid-like follicular carcinoma of the kidney remains controversial. We collected 8 cases of this purported "atrophic kidney"-like lesion to fully describe their clinical and histologic spectrum, their possible etiology, and to discuss their distinction from other renal neoplasms. Eight total cases were identified with patient ages ranging from 9 to 48 years (mean: 29 y; median: 28.5 y). Four patients were female and 4 were male. The tumors were unifocal and size ranged from 1.6 to 4.9 cm (mean: 3.4 cm; median: 3.4 cm). All 8 tumors had a remarkably similar histology. Each was enveloped by a smooth muscle rich capsule and had an overall low power "follicular" architecture. The luminal spaces of the "follicles" (or cysts) contained eosinophilic secretions and the lining epithelium was often flattened and atrophic, but some had more rounded cells with a distinctive hobnail arrangement. Many cysts contained discohesive round cells floating within the eosinophilic material, and some contained small intraluminal tufts with features of markedly atrophic glomeruli. Periodic acid-Schiff stains highlighted basement membrane material extending into these glomerular-like tufts, and some contained small distinct capillaries surrounded by endothelial cells, interspersed mesangial-like cells, and rare surrounding podocyte-like cells, providing additional evidence for glomerulocystic structures. Scattered calcifications were present within cysts (or within cyst walls) in varying numbers and were characterized by 2 types: psammoma body-like or more amorphous deposits. The tissue between cystic glomeruli contained predominantly small atrophic tubular structures, but collagenized stroma and smaller collapsed glomeruli were also present. The 2 tumors from the oldest 2 patients (48 and 39 y) had a more striking degree of stromal hyalinization. Immunohistochemically, the cyst lining cells had a predominant WT-positive/PAX-8 negative/CK7-negative phenotype, while tubules were typically WT-1 negative/PAX-8 positive/CK7-positive. Upon comparison to a control group of 10 kidneys containing incidental non-mass-forming glomerulocystic change, the morphologic features and immunophenotype were identical. To date, no patient has had any recurrence or aggressive clinical behavior based on follow status in 7 of 8 cases (follow-up range: 9 to 168 mo; median: 24 mo; mean: 40 mo). In summary, we describe the clinicopathologic features of 8 unique, benign "atrophic kidney"-like lesions that may simply represent a non-neoplastic form of organizing tubular atrophy and glomerulocystic change, and emphasize their distinction from thyroid-like follicular carcinoma of the kidney.

Histological and molecular characterization of TFEB-rearranged renal cell carcinomas

The 2016 WHO Classification of Tumors of the Urinary System recognizes microphthalmia transcription factor (MiT) family translocation carcinomas as a separate entity among renal cell carcinomas. TFE3 and transcription factor EB (TFEB) are members of the MiT family for which chromosomal rearrangements have been associated with renal cell carcinoma formation. TFEB translocation renal cell carcinoma is a rare tumor harboring a t(6;11)(p21;q12) translocation. Recently, renal cell carcinomas with TFEB amplification have been identified. TFEB amplified renal cell carcinomas have to be distinguished from TFEB-translocated renal cancer, because they may demonstrate a more aggressive behavior. Herein, we present a TFEB-translocated and a TFEB-amplified carcinoma cases and describe their distinct histological, immunohistochemical, and molecular characteristics. In addition, we review conventional morphology, immunophenotype, genetic background, and clinical outcome of TFEB-rearranged RCCs in the literature, with a special emphasis on important differential diagnoses and the diagnostic approach.

New entities, new technologies, new findings: A review of the cytologic features of recently established subtypes of renal cell carcinoma

Several new renal tumor types with distinctive pathologic, epidemiologic, and genetic signatures have recently been adopted in the fourth edition of the World Health Organization classification. In succeeding years, the cytologic features of most of these new types have been described, adding to the trend of increasing diagnostic accuracy for most common renal cell carcinoma subtypes and the important diagnostic role of cytologic sampling in the management and personalization of therapy. The current article reviews the cytologic findings from these recently established renal cell carcinoma subtypes. Emphasis is placed on cytologic diagnostic clues, confirmatory ancillary testing, salient differential diagnoses, and challenges that can be encountered in an attempt to render accurate interpretations in small samples.

t(6;11) renal cell carcinoma: a study of seven cases including two with aggressive behavior, and utility of CD68 (PG-M1) in the differential diagnosis with pure epithelioid PEComa/epithelioid angiomyolipoma

Renal cell carcinomas with t(6;11) chromosome translocation involving the TFEB gene are indolent neoplasms which often occur in young patients. In this study, we report seven cases of renal cell carcinoma with TFEB rearrangement, two of whom had histologically proven metastasis. Patients (4F, 3M) ranged in age from 19 to 55 years (mean 37). One patient developed paratracheal and pleural metastases 24 months after surgery and died of disease after 46 months; another one recurred with neoplastic nodules in the perinephric fat and pelvic soft tissue. Histologically, either cytological or architectural appearance was peculiar in each case whereas one tumor displayed the typical biphasic morphology. By immunohistochemistry, all tumors labelled for cathepsin K, Melan-A and CD68 (KP1 clone). HMB45 and PAX8 staining were detected in six of seven tumors. All tumors were negative for CD68 (PG-M1 clone), CKAE1-AE3, CK7, CAIX, and AMACR. Seven pure epithelioid PEComa/epithelioid angiomyolipomas, used as control, were positive for cathepsin K, melanocytic markers, and CD68 (PG-M1 and KP1) and negative for PAX8. Fluorescence in situ hybridization results showed the presence of TFEB gene translocation in all t(6;11) renal cell carcinomas with a high frequency of split TFEB fluorescent signals (mean 74%). In the primary and metastatic samples of the two aggressive tumors, increased gene copy number was observed (3-5 fluorescent signals per neoplastic nuclei) with a concomitant increased number of CEP6. Review of the literature revealed older age and larger tumor size as correlating with aggressive behavior in these neoplasms. In conclusion, we present the clinical, morphological and molecular features of seven t(6;11) renal cell carcinomas, two with histologically demonstrated metastasis. We report the high frequency of split signals by FISH in tumors with t(6;11) chromosomal rearrangement and the occurrence of TFEB gene copy number gains in the aggressive cases, analyzing either the primary or metastatic tumor. Finally, we demonstrate the usefulness of CD68 (PG-M1) immunohistochemical staining in distinguishing t(6;11) renal cell carcinoma from pure epithelioid PEComa/epithelioid angiomyolipoma.

Novel gene fusion of PRCC-MITF defines a new member of MiT family translocation renal cell carcinoma: clinicopathological analysis and detection of the gene fusion by RNA sequencing and FISH

AIMS

MITF, TFE3, TFEB and TFEC belong to the same microphthalmia-associated transcription factor family (MiT). Two transcription factors in this family have been identified in two unusual types of renal cell carcinoma (RCC): Xp11 translocation RCC harbouring TFE3 gene fusions and t(6;11) RCC harbouring a MALAT1-TFEB gene fusion. The 2016 World Health Organisation classification of renal neoplasia grouped these two neoplasms together under the category of MiT family translocation RCC. RCCs associated with the other two MiT family members, MITF and TFEC, have rarely been reported. Herein, we identify a case of MITF translocation RCC with the novel PRCC-MITF gene fusion by RNA sequencing.

METHODS AND RESULTS

Histological examination of the present tumour showed typical features of MiT family translocation RCCs, overlapping with Xp11 translocation RCC and t(6;11) RCC. However, this tumour showed negative results in TFE3 and TFEB immunochemistry and split fluorescence in-situ hybridisation (FISH) assays. The other MiT family members, MITF and TFEC, were tested further immunochemically and also showed negative results. RNA sequencing and reverse transcription-polymerase chain reaction confirmed the presence of a PRCC-MITF gene fusion: a fusion of PRCC exon 5 to MITF exon 4. We then developed FISH assays covering MITF break-apart probes and PRCC-MITF fusion probes to detect the MITF gene rearrangement.

CONCLUSIONS

This study both proves the recurring existence of MITF translocation RCC and expands the genotype spectrum of MiT family translocation RCCs.

Detection of 6 TFEB-amplified renal cell carcinomas and 25 renal cell carcinomas with MITF translocations: systematic morphologic analysis of 85 cases evaluated by clinical TFE3 and TFEB FISH assays

Renal cell carcinomas with MITF aberrations demonstrate a wide morphologic spectrum, highlighting the need to consider these entities within the differential diagnosis of renal tumors encountered in clinical practice. Herein, we describe our experience with application of clinical fluorescence in situ hybridization (FISH) assays for detection of TFE3 and TFEB gene aberrations from 85 consecutive renal cell carcinoma cases submitted to our genitourinary FISH service. Results from 170 FISH assays performed on these tumors were correlated with available clinicopathologic findings. Ninety-eight percent of renal tumors submitted for FISH evaluation were from adult patients. Thirty-one (37%) tumors were confirmed to demonstrate MITF aberrations (21 TFE3 translocation, 4 TFEB translocation, and 6 TFEB amplification cases). Overall, renal cell carcinomas with MITF aberrations demonstrated morphologic features overlapping with clear cell, papillary, or clear cell papillary renal cell carcinomas. Renal cell carcinomas with MITF aberrations were significantly more likely to demonstrate dual (eosinophilic and clear) cytoplasmic tones (P=0.030), biphasic TFEB translocation renal cell carcinoma-like morphology (P=0.002), psammomatous calcifications (P=0.002), and nuclear pseudoinclusions (P=0.001) than renal cell carcinomas without MITF aberrations. Notably, 7/9 (78%) renal cell carcinomas exhibiting subnuclear clearing and linear nuclear array (6 of which showed high World Health Organization/International Society of Urological Pathology nucleolar grade) demonstrated TFE3 translocation, an association that was statistically significant when compared with renal cell carcinomas without MITF aberrations (P=0.009). In this cohort comprising consecutive cases, TFEB-amplified renal cell carcinomas were more commonly identified than renal cell carcinomas with TFEB translocations, and four (67%) of these previously unreported TFEB-amplified renal cell carcinomas demonstrated oncocytic and papillary features with a high World Health Organization/International Society of Urological Pathology nucleolar grade. In summary, TFE3 and TFEB FISH evaluation aids in identification and accurate classification of renal cell carcinomas with MITF aberrations, including TFEB-amplified renal cell carcinoma, which may demonstrate aggressive behavior.

PRCC-TFE3 dual-fusion FISH assay: A new method for identifying PRCC-TFE3 renal cell carcinoma in paraffin-embedded tissue

PRCC-TFE3 renal cell carcinoma (RCC) is one of the most common types of Xp11.2 translocation renal cell carcinoma (tRCC), of which the diagnosis mainly relies on reverse transcription-polymerase chain reaction (RT-PCR) or chromosomal analysis in fresh frozen samples. Herein, we developed a new dual-fusion fluorescence in situ hybridization (FISH) probe to succinctly identify PRCC-TFE3 RCC in paraffin-embedded tissue. We immunohistochemically analyzed TFE3 and cathepsin K expression in 23 cases of Xp11.2 tRCC which had been confirmed by break-apart TFE3 FISH probe. Next, the dual-fusion FISH assay was performed on these selected cases. Twenty typical cases of clear renal cell carcinoma and 20 cases of papillary renal cell carcinoma were collected as control groups. Seven cases were finally confirmed as PRCC-TFE3 RCC by FISH detection, emerging dual-fusion signals, of which 2 cases were identified as PRCC-TFE3 RCC by RT-PCR previously. All remaining cases were negative for the PRCC-TFE3 rearrangement by FISH. The TFE3 immunohistochemistry was positive in 22/23 cases and the cathepsin K was positive in 16/23 cases. All 7 PRCC-TFE3 RCCs showed positive cathepsin K immunoreactivity. Our results reveal that PRCC-TFE3 dual-fusion FISH probe is an efficient and concise technique for diagnosing PRCC-TFE3 RCC in paraffin-embedded tissue.

Melanotic MiT family translocation neoplasms: Expanding the clinical and molecular spectrum of this unique entity of tumors

MiT family translocation tumors are a group of neoplasms characterized by translocations involving MiT family transcription factors. The translocation renal cell carcinomas, TFE3 (Xp11.2) and TFEB (t6;11) are known members of this family. Melanotic Xp11 translocation renal cancer is a more recently described entity. To date only 14 cases have been described. It is characterized by a distinct set of features including a nested epithelioid morphology, melanin pigmentation, labeling for markers of melanocytic differentiation, lack of labeling for markers of renal tubular differentiation, predominance in a younger age population and association with aggressive clinical behavior. There are noted similarities between that entity and TFE3 associated PEComas. There are no cases reported of equivalent melanotic TFEB translocation renal cancer. We report 2 rare cases of melanotic translocation renal neoplasms. The first is a melanotic TFE3 translocation renal cancer with an indolent clinical course, occurring in a patient more than 3-decades older than the usual average age in which such tumors have been described. The other case is, to our knowledge, the first reported melanotic TFEB translocation cancer of the kidney. Both cases exhibit the same H&E morphology as previously reported in melanotic translocation renal cancers and label accordingly with HMB45 and Melan-A. While the TFE3 melanotic tumor lacked any evidence of renal tubular differentiation, the TFEB melanotic cancer exhibited some staining for renal tubular markers. Based on the unique features noted above, these two cases expand the clinical and molecular spectrum of the melanotic translocation renal cancers.

Renal Cell Carcinoma With Chromosome 6p Amplification Including the TFEB Gene: A Novel Mechanism of Tumor Pathogenesis?

Amplification of chromosome 6p has been implicated in aggressive behavior in several cancers, but has not been characterized in renal cell carcinoma (RCC). We identified 9 renal tumors with amplification of chromosome 6p including the TFEB gene, 3 by fluorescence in situ hybridization, and 6 from the Cancer Genome Atlas (TCGA) databases. Patients' ages were 28 to 78 years (median, 61 y). Most tumors were high stage (7/9 pT3a, 2/9 pN1). Using immunohistochemistry, 2/4 were positive for melanocytic markers and cathepsin K. Novel TFEB fusions were reported by TCGA in 2; however, due to a small composition of fusion transcripts compared with full-length transcripts (0.5/174 and 3.3/132 FPKM), we hypothesize that these represent secondary fusions due to amplification. Five specimens (4 TCGA, 1 fluorescence in situ hybridization) had concurrent chromosome 3p copy number loss or VHL deletion. However, these did not resemble clear cell RCC, had negative carbonic anhydrase IX labeling, lacked VHL mutation, and had papillary or unclassified histology (2/4 had gain of chromosome 7 or 17). One tumor each had somatic FH mutation and SMARCB1 mutation. Chromosome 6p amplification including TFEB is a previously unrecognized cytogenetic alteration in RCC, associated with heterogenous tubulopapillary eosinophilic and clear cell histology. The combined constellation of features does not fit cleanly into an existing tumor category (unclassified), most closely resembling papillary or translocation RCC. The tendency for high tumor stage, varied tubulopapillary morphology, and a subset with melanocytic marker positivity suggests the possibility of a unique tumor type, despite some variation in appearance and genetics.

TFEB-amplified Renal Cell Carcinomas: An Aggressive Molecular Subset Demonstrating Variable Melanocytic Marker Expression and Morphologic Heterogeneity

Renal cell carcinomas (RCCs) with the t(6;11)(p21;q12) chromosome translocation are low-grade RCC which often occur in young patients. They typically feature an unusual biphasic morphology characterized by nests of larger epithelioid cells surrounding intraluminal collections of smaller cells clustered around basement membrane material. The t(6;11)(p21;q12) translocation fuses the Alpha (MALAT1) gene with the TFEB transcription factor gene, resulting in upregulated expression of intact native TFEB that drives the aberrant expression of melanocytic markers which is a hallmark of this distinctive neoplasm. We now report 8 cases of RCC, which demonstrate TFEB gene amplification (6 without TFEB rearrangement, 2 with concurrent TFEB rearrangement) and demonstrate downstream consequences of TFEB overexpression. Like the unamplified t(6;11) RCC, all TFEB-amplified RCC were associated with aberrant melanocytic marker expression. However, several differences between TFEB-amplified RCC and the usual unamplified t(6;11) RCC are evident. First, TFEB-amplified RCC occurred in older patients (median age, 64.5 y) compared with unamplified t(6;11) RCC (median age, 31 y). Second, the morphology of TFEB-amplified RCC is not entirely distinctive, frequently featuring nests of high-grade epithelioid cells with eosinophilic cytoplasm associated with pseudopapillary formation and necrosis, or true papillary formations. These patterns raise the differential diagnosis of high-grade clear cell and papillary RCC. Third, TFEB and melanocytic marker expression was more variable within the TFEB-amplified RCC. TFEB protein expression by immunohistochemistry was detectable in 6 of 8 cases. While all 8 cases expressed melan-A, only 5 of 8 expressed cathepsin K and only 3 of 8 expressed HMB45. Fourth, the TFEB-amplified RCC were associated with a more aggressive clinical course; 3 of 8 cases presented with advanced stage or metastatic disease, 2 subsequently developed metastatic disease, whereas the other 3 cases had minimal/no follow-up. Our results are corroborated by scant data reported on 6 TFEB-amplified RCC in the literature, gleaned from 1 case report, 1 abstract, and 4 individual cases identified within 2 genomic studies of large cohorts of RCC. In summary, TFEB-amplified RCC represent a distinct molecular subtype of high-grade adult RCC associated with aggressive clinical behavior, variable morphology, and aberrant melanocytic marker expression.

SFPQ/PSF-TFE3 renal cell carcinoma: a clinicopathologic study emphasizing extended morphology and reviewing the differences between SFPQ-TFE3 RCC and the corresponding mesenchymal neoplasm despite an identical gene fusion

Xp11 translocation renal cell carcinoma (RCC) with SFPQ/PSF-TFE3 gene fusion is a rare epithelial tumor. Of note, the appearance of the gene fusion does not necessarily mean that it is renal cell carcinoma. The corresponding mesenchymal neoplasms, including Xp11 neoplasm with melanocytic differentiation, TFE3 rearrangement-associated perivascular epithelioid cell tumor (PEComa) and melanotic Xp11 translocation renal cancer, can also harbor the identical gene fusion. However, the differences between Xp11 translocation RCC and the corresponding mesenchymal neoplasm have only recently been described. Herein, we examined 5 additional cases of SFPQ-TFE3 RCCs using clinicopathologic, immunohistochemical, and molecular analyses. One tumor had the typical morphologic features of SFPQ-TFE3 RCC, whereas other 3 cases demonstrated the unusual morphologic features associated with pseudorosettes formation or clusters of smaller cells, mimicking TFEB RCC. The remaining one showed branching tubules and papillary structure composed of clear and eosinophilic tumor cells. Immunohistochemically, all 5 cases demonstrated moderate (2+) or strong (3+) positive staining for TFE3, PAX-8 and CD10, whereas no cases demonstrated TFEB, Cathepsin K, CA-IX, CK7, Melan-A, or HMB-45 expression. Genetically, the fusion transcripts were identified in 3 cases by reverse-transcription polymerase chain reaction (RT-PCR). On the basis of fluorescence in situ hybridization (FISH) analysis, all the cases were detected with SFPQ-TFE3 gene fusion. Clinical follow-up data were available for all the patients, and no one developed tumor recurrence, progression, or metastasis. We also review the differences between SFPQ-TFE3 RCC and the corresponding mesenchymal neoplasm despite the identical gene fusion. The presence of pseudorosettes also expands the known histological features of SFPQ-TFE3 RCC.

Xp11.2 translocation renal cell carcinoma with NONO-TFE3 gene fusion: morphology, prognosis, and potential pitfall in detecting TFE3 gene rearrangement

Xp11 translocation renal cell carcinomas are characterized by several different translocations involving the TFE3 gene. Tumors with different specific gene fusions may have different clinicopathological manifestations. Fewer than 10 renal cell carcinoma cases with NONO-TFE3 have been described. Here we examined eight additional cases of this rare tumor using clinicopathological, immunohistochemical, and molecular analyses. The male-to-female ratio of our study cohort was 1:1, and the median age was 30 years. The most distinctive feature of the tumors was that they exhibited glandular/tubular or papillary architecture that was lined with small-to-medium cuboidal to high columnar cells with indistinct cell borders and an abundantly clear or flocculent eosinophilic cytoplasm. The nuclei were oriented toward the luminal surface and were round and uniform in shape, which resulted in the appearance of secretory endometrioid subnuclear vacuolization. The distinct glandular/tubular or papillary architecture was often accompanied by sheets of epithelial cells that presented a biphasic pattern. Immunohistochemically, all eight cases demonstrated moderate (2+) or strong (3+) positive staining for TFE3, CD10, RCC marker, and PAX-8. None of the tumors were immunoreactive for CK7, Cathepsin K, Melan-A, HMB45, Ksp-cadherin, Vimentin, CA9, 34βE12 or CD117. NONO-TFE3 fusion transcripts were identified in six cases by RT-PCR. All eight cases showed equivocal split signals with a distance of nearly 2 signal diameters and sometimes had false-negative results. Furthermore, we developed a fluorescence in situ hybridization (FISH) assay to serve as an adjunct diagnostic tool for the detection of the NONO-TFE3 fusion gene and used this method to detect the fusion gene in all eight cases. Long-term follow-up (range, 10-102 months) was available for 7 patients. All 7 patients were alive with no evidence of recurrent disease or disease progression after their initial resection. This report adds to the known data regarding NONO-TFE3 renal cell carcinoma.

Fluorescence in situ hybridization in surgical pathology: principles and applications

Identification of recurrent tumour‐specific chromosomal translocations and novel fusion oncogenes has important diagnostic, therapeutic and prognostic implications. Over the past decade, fluorescence in situ hybridization (FISH) analysis of tumour samples has been one of the most rapidly growing areas in genomic medicine and surgical pathology practice. Unlike traditional cytogenetics, FISH affords a rapid analysis of formalin‐fixed, paraffin‐embedded cells within a routine pathology practice workflow. As more diagnostic and treatment decisions are based on results of FISH, demand for the technology will become more widespread. Common FISH‐detected alterations are chromosome deletions, gains, translocations, amplifications and polysomy. These chromosome alterations may have diagnostic and therapeutic implications for many tumour types. Integrating genomic testing into cancer treatment decisions poses many technical challenges, but rapid progress is being made to overcome these challenges in precision medicine. FISH assessment of chromosomal changes relevant to differential diagnosis and cancer treatment decisions has become an important tool for the surgical pathologist. The aim of this review is to provide a theoretical and practical survey of FISH detected translocations with a focus on strategies for clinical application in surgical pathology practice.

[The translocation carcinoma: A pediatric renal tumor also in adults]

The MiT family of translocation-associated renal cell carcinomas comprise approximately 40 % of renal cell carcinomas in young patients but only up to 4 % of renal cell carcinomas in adult patients. The Xp11.2 translocation-associated tumors are the most frequent and were included in the 2004 World Health Organization (WHO) classification. They contain a fusion of the TFE3 gene with ASPSCR1, PRCC, NONO, SPFQ or CLTC resulting in an immunohistochemically detectable nuclear overexpression of TFE3. The Xp11.2 translocation-associated renal cell carcinomas are characterized by ample clear cytoplasm, papillary architecture and abundant psammoma bodies. The TFEB translocation-associated renal cell carcinomas are much rarer and show a biphasic architecture. Fluorescence in situ hybridization permits the detection of a translocation by means of a break apart probe for the TFE3 and TFEB genes and is recommended for the diagnosis of renal cell carcinomas in patients under 30 years of age. The TFE3 and TFEB translocation-associated tumors are classified as MiT family translocation carcinomas in the new WHO classification.The rare renal cell carcinomas harboring an ALK rearrangement with fusion to VCL in young patients with sickle cell trait show a characteristic morphology and are listed in the new WHO classification as a provisional entity.

BRM/SMARCA2-negative clear cell renal cell carcinoma is associated with a high percentage of BRM somatic mutations, deletions and promoter methylation

AIMS

The aim of this study was to investigate potential molecular mechanisms associated with loss of BRM expression in poorly differentiated clear cell renal cell carcinoma (ccRCC).

METHODS AND RESULTS

Nineteen previously selected BRM-negative RCC tissues were examined by DNA sequencing, fluorescence in-situ hybridization (FISH) and methylation-specific polymerase chain reaction (PCR) of the BRM gene. BRM mutation was identified in 78.9% (15 of 19) cases, chromosome 9 monosomy or BRM deletion in 43.8% (seven of 16) and BRM promoter region cytosine-phosphate-guanine (CpG) methylation in 42.8% (six of 14). These results indicated that 89.5% (17 of 19) of the cases harboured at least one type of BRM genetic alteration, with two or more types of alteration in 47.4% (nine of 19). Such alterations were found rarely in adjacent non-neoplastic tissues and low-grade areas of composite tumours.

CONCLUSIONS

BRM gene mutation, chromosome 9 monosomy or BRM deletion and CpG methylation contribute collectively to the loss of BRM expression in ccRCC. This work focusing on composite tumours indicated that BRM abnormality occurred during tumour progression.

Extended immunologic and genetic lineage of mammary analogue secretory carcinoma of salivary glands

Mammary analogue secretory carcinoma (MASC) of salivary glands is a newly recognized tumor entity. To explore a more practical and convenient immunohistochemical approach to distinguish MASC from other tumors arising from salivary glands as well as to expand the immunologic and genetic lineage of MASC, we examined 17 MASCs using clinicopathologic, immunohistochemical, and molecular analyses. Eighteen cases of acinic cell carcinoma, 18 cases of adenoid cystic carcinoma, 22 cases of mucoepidermoid carcinoma, and 14 cases of basal cell adenocarcinoma were brought in for comparison. Seventeen MASCs shared similar architectures with not only intraluminal or intracellular secretion but also low-grade vesicular nuclei. In addition, they were all immunoreactive for S-100 and SOX-10, whereas only 3 of 17 demonstrated reactivity for GATA-3 and P63, and 4 of 17 were focally positive for CD117. ETV6 translocation was detected in 10 cases by fluorescence in situ hybridization, whereas intact ETV6 was noted in 2 cases. Our data proposed a combined immunohistochemical panel to distinguish MASC from other tumors arising from salivary glands and expanded the immunologic and genetic lineage of MASC.

Modelling TFE renal cell carcinoma in mice reveals a critical role of WNT signaling

TFE-fusion renal cell carcinomas (TFE-fusion RCCs) are caused by chromosomal translocations that lead to overexpression of the TFEB and TFE3 genes (Kauffman et al., 2014). The mechanisms leading to kidney tumor development remain uncharacterized and effective therapies are yet to be identified. Hence, the need to model these diseases in an experimental animal system (Kauffman et al., 2014). Here, we show that kidney-specific TFEB overexpression in transgenic mice, resulted in renal clear cells, multi-layered basement membranes, severe cystic pathology, and ultimately papillary carcinomas with hepatic metastases. These features closely recapitulate those observed in both TFEB- and TFE3-mediated human kidney tumors. Analysis of kidney samples revealed transcriptional induction and enhanced signaling of the WNT β-catenin pathway. WNT signaling inhibitors normalized the proliferation rate of primary kidney cells and significantly rescued the disease phenotype in vivo. These data shed new light on the mechanisms underlying TFE-fusion RCCs and suggest a possible therapeutic strategy based on the inhibition of the WNT pathway.

Molecular genetics and immunohistochemistry characterization of uncommon and recently described renal cell carcinomas

Renal cell carcinoma (RCC) compromises multiple types and has been emerging dramatically over the recent several decades. Advances and consensus have been achieved targeting common RCCs, such as clear cell carcinoma, papillary RCC and chromophobe RCC. Nevertheless, little is known on the characteristics of several newly-identified RCCs, including clear cell (tubulo) papillary RCC, Xp11 translocation RCC, t(6;11) RCC, succinate dehydrogenase (SDH)-deficient RCC, acquired cystic disease-associated RCC, hereditary leiomyomatosis RCC syndrome-associated RCC, ALK translocation RCC, thyroid-like follicular RCC, tubulocystic RCC and hybrid oncocytic/chromophobe tumors (HOCT). In current review, we will collect available literature of these newly-described RCCs, analyze their clinical pathologic characteristics, discuss their morphologic and immunohistologic features, and finally summarize their molecular and genetic evidences. We expect this review would be beneficial for the understanding of RCCs, and eventually promote clinical management strategies.

Xp11 neoplasm with melanocytic differentiation of the prostate harbouring the novel NONO-TFE3 gene fusion: report of a unique case expanding the gene fusion spectrum

Recently, an increasing number of TFE3 rearrangement-associated tumours have been reported, such as TFE3 rearrangement-associated perivascular epithelioid cell tumours (PEComas), melanotic Xp11 translocation renal cancers and melanotic Xp11 neoplasms. We have suggested that these tumours belong to a single clinicopathological spectrum. 'Xp11 neoplasm with melanocytic differentiation' or 'melanotic Xp11 neoplasm' have been proposed to designate this unique neoplasm. Herein, we describe the first case of an Xp11 neoplasm with melanocytic differentiation to be described in the prostate, bearing the novel NONO-TFE3 gene fusion. This study both adds to the spectrum regarding melanotic Xp11 neoplasms and expands its gene fusion spectrum. Moreover, we discuss the relationship of these rare tumours to neoplasms such as conventional PEComas, alveolar soft part sarcomas, malignant melanomas, clear cell sarcomas and Xp11 translocation renal cancers.

Diagnosis of adults Xp11.2 translocation renal cell carcinoma by immunohistochemistry and FISH assays: clinicopathological data from ethnic Chinese population

This study aimed to assess the utility of transcription factor E3 (TFE3) break-apart fluorescence in situ hybridization (FISH) assay in diagnosis of Xp11.2 translocation renal cell carcinoma (Xp11.2 RCC) and to compare the clinicopathological features between adult Xp11.2 RCC and non-Xp11.2 RCC. 76 pathologically suspected Xp11.2 RCCs were recruited from our institution. Both TFE3 immunohistochemistry (IHC) and TFE3 FISH assay were performed for the entire cohort. The progression-free survival (PFS) and overall survival (OS) curves were estimated using the Kaplan-Meier method. FISH analysis confirmed 30 Xp11.2 RCCs, including 28 cases with positive TFE3 immunostaining and 2 cases with negative immunostaining. The false-positive and false-negative rates were 6.7% (2/30) and 4.3% (2/46), respectively, for TFE3 IHC compared with FISH assay. Xp11.2 RCC was significantly associated with higher pathological stage and Fuhrman nuclear grade compared with non-Xp11.2 RCC (P < 0.05). The median PFS and OS for TFE3 FISH-positive group were 13.0 months (95% CI, 8.4–17.6 months) and 50.0 months (95% CI, 27.6–72.4 months), respectively, while the median PFS and OS had not been reached for TFE3 FISH-negative group. In conclusion, TFE3 break-apart FISH assay is a highly useful and standard diagnostic method for Xp11.2 RCC. Adult Xp11.2 RCC is clinically aggressive and often presents at advanced stage with poor prognosis.

Translocational renal cell carcinoma (t(6;11)(p21;q12) with transcription factor EB (TFEB) amplification and an integrated precision approach: a case report

INTRODUCTION

Renal cell carcinoma with the distinct type of t(6;11)(p21;q12) translocation (transcription factor EB) is a rare neoplasm. In the present case study, we show for the first time an autophagy signature in a patient with transcription factor EB renal cell carcinoma. We attempted to characterize the mutational and expressional features of a t(6;11)(p21;q12) renal cell carcinoma, in an effort to address the potential for molecular guidance of personalized medical decision for a case in this renal cell carcinoma category.

CASE PRESENTATION

We report the case of a 42-year-old white man who had a late relapse of his renal cell carcinoma. The first diagnosis of clear cell renal carcinoma was derived from a histological examination; analyzing the metastasis and going back to the primary tumor it turned out to be a transcription factor EB-renal cell carcinoma. The treatment plan included local radiation and systemic therapy. As part of the multimodal approach, tumor samples for genetic assessment were obtained. However, there is no recommended standard therapy for transcription factor EB-renal cell carcinoma. Despite four lines of medical treatment with targeted therapy and one checkpoint inhibitor, all attempts to prolong the patient's survival failed.

CONCLUSIONS

During the course of this unusual disease, we gained insights which, to the best of our knowledge, were unknown before in the expression of the gene signature linked to autophagy. This might in part explain the resistance to conventional targeted therapy acknowledged in our patient.

Emerging Entities in Renal Neoplasia

This article reviews emerging entities in renal epithelial neoplasia, including tubulocystic carcinoma, clear-cell-papillary renal cell carcinoma (RCC), thyroid-like follicular RCC, ALK-related RCC, translocation RCC, acquired cystic disease-related RCC, succinate dehydrogenase-deficient RCC, and hereditary leiomyomatosis-RCC syndrome-associated RCC. Many of these rarer subtypes of RCC were recently studied in more depth and are included in the upcoming version of the World Health Organization classification of tumors. Emphasis is placed on common gross and morphologic features, differential diagnoses, use of ancillary studies for making accurate diagnoses, molecular alterations, and predicted biologic behavior based on previous studies.

PSF/SFPQ is a very common gene fusion partner in TFE3 rearrangement-associated perivascular epithelioid cell tumors (PEComas) and melanotic Xp11 translocation renal cancers: clinicopathologic, immunohistochemical, and molecular characteristics suggesting classification as a distinct entity

An increasing number of TFE3 rearrangement-associated tumors, such as TFE3 rearrangement-associated perivascular epithelioid cell tumors (PEComas), melanotic Xp11 translocation renal cancers, and melanotic Xp11 neoplasms, have recently been reported. We examined 12 such cases, including 5 TFE3 rearrangement-associated PEComas located in the pancreas, cervix, or pelvis and 7 melanotic Xp11 translocation renal cancers, using clinicopathologic, immunohistochemical, and molecular analyses. All the tumors shared a similar morphology, including a purely nested or sheet-like architecture separated by a delicate vascular network, purely epithelioid cells displaying a clear or granular eosinophilic cytoplasm, a lack of papillary structures and spindle cell or fat components, uniform round or oval nuclei containing small visible nucleoli, and, in most cases (11/12), melanin pigmentation. The levels of mitotic activity and necrosis varied. All 12 cases displayed moderately (2+) or strongly (3+) positive immunoreactivity for TFE3 and cathepsin K. One case labeled focally for HMB45 and Melan-A, whereas the others typically labeled moderately (2+) or strongly (3+) for 1 of these markers. None of the cases were immunoreactive for smooth muscle actin, desmin, CKpan, S100, or PAX8. PSF-TFE3 fusion genes were confirmed by reverse transcription polymerase chain reaction in cases (7/7) in which a novel PSF-TFE3 fusion point was identified. All of the cases displayed TFE3 rearrangement associated with Xp11 translocation. Furthermore, we developed a PSF-TFE3 fusion fluorescence in situ hybridization assay for the detection of the PSF-TFE3 fusion gene and detected it in all 12 cases. Clinical follow-up data were available for 7 patients. Three patients died, and 2 patients (cases 1 and 3) remained alive with no evidence of disease after initial resection. Case 2 experienced recurrence and remained alive with disease. Case 5, a recent case, remained alive with extensive abdominal cavity metastases. Our data suggest that these tumors belong to a single clinicopathologic spectrum and expand the known characteristics of TFE3 rearrangement-associated tumors.

Pediatric Papillary Renal Cell Carcinoma in a Horseshoe Kidney: A Case Report with Review of the Literature

Renal cell carcinoma is the most common malignancy of the kidney in adults. In children, however, it only accounts for an estimated 1.8 to 6.3% of all pediatric malignant renal tumors. Papillary renal cell carcinoma is the second most common type of renal cell carcinoma in children. We present the case of a 12-year-old boy with a 2-month history of abdominal pain, unexplained weight loss, and gross hematuria. Computed tomography revealed a horseshoe kidney and a well-defined mass of 4 cm arising from the lower pole of the right kidney. Microscopically the tumor was composed of papillae covered with cells with abundant eosinophilic cytoplasm and high-grade nuclei with prominent nucleoli. Immunohistochemistry was performed; EMA, Vimentin, and AMACR were strongly positive while CK7, CD10, RCC antigen, TFE3, HMB-45, and WT-1 were negative. Currently, 10 months after the surgical procedure, the patient remains clinically and radiologically disease-free.

Renal cell carcinomas with t(6;11) (p21;q12): presentation of two cases with computed tomography findings

Renal cell carcinomas with t(6;11) (p21;q12) translocation are extremely rare and primarily affect children and young adults. To our knowledge, there has been no case report focusing on the imaging manifestations in the existing literature. Hence, we describe the computed tomography findings of two young adults.

MiT family translocation renal cell carcinoma

The MiT subfamily of transcription factors includes TFE3, TFEB, TFC, and MiTF. Gene fusions involving two of these transcription factors have been identified in renal cell carcinoma (RCC). The Xp11 translocation RCCs were first officially recognized in the 2004 WHO renal tumor classification, and harbor gene fusions involving TFE3. The t(6;11) RCCs harbor a specific Alpha-TFEB gene fusion and were first officially recognized in the 2013 International Society of Urologic Pathology (ISUP) Vancouver classification of renal neoplasia. These two subtypes of translocation RCC have many similarities. Both were initially described in and disproportionately involve young patients, though adult translocation RCC may overall outnumber pediatric cases. Both often have unusual and distinctive morphologies; the Xp11 translocation RCCs frequently have clear cells with papillary architecture and abundant psammomatous bodies, while the t(6;11) RCCs frequently have a biphasic appearance with both large and small epithelioid cells and nodules of basement membrane material. However, the morphology of these two neoplasms can overlap, with one mimicking the other. Both of these RCCs underexpress epithelial immunohistochemical markers like cytokeratin and epithelial membrane antigen (EMA) relative to most other RCCs. Unlike other RCCs, 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, on the basis of clinical, morphologic, immunohistochemical, and genetic similarities, the 2013 ISUP Vancouver classification of renal neoplasia grouped these two neoplasms together under the heading of "MiT family translocation RCC." This review summarizes our current knowledge of these recently described RCCs.

Activators of G protein signaling in the kidney

Heterotrimeric G proteins play a crucial role in regulating signal processing to maintain normal cellular homeostasis, and subtle perturbations in its activity can potentially lead to the pathogenesis of renal disorders or diseases. Cell-surface receptors and accessory proteins, which normally modify and organize the coupling of individual G protein subunits, contribute to the regulation of heterotrimeric G protein activity and their convergence and/or divergence of downstream signaling initiated by effector systems. Activators of G protein signaling (AGS) are a family of accessory proteins that intervene at multiple distinct points during the activation-inactivation cycle of G proteins, even in the absence of receptor stimulation. Perturbations in the expression of individual AGS proteins have been reported to modulate signal transduction pathways in a wide array of diseases and disorders within the brain, heart, immune system, and more recently, the kidney. This review will provide an overview of the expression profile, localization, and putative biologic role of the AGS family in the context of normal and diseased states of the kidney.