Histological and molecular characterization of TFEB-rearranged renal cell carcinomas

A rare case of TFEB/6p21/VEGFA-amplified renal cell carcinoma diagnosed by whole-exome sequencing: clinicopathological and genetic feature report and literature review

BACKGROUND

TFEB/6p21/VEGFA-amplified renal cell carcinoma (RCC) is rare and difficult to diagnose, with diverse histological patterns and immunohistochemical and poorly defined molecular genetic characteristics.

CASE PRESENTATION

We report a case of a 63-year-old male admitted in 2017 with complex histomorphology, three morphological features of clear cell, eosinophilic and papillary RCC and resembling areas of glomerular and tubular formation. The immunophenotype also showed a mixture of CD10 and P504s. RCC with a high suspicion of collision tumors was indicated according to the 2014 WHO classification system; no precise diagnosis was possible. The patient was diagnosed at a different hospital with poorly differentiated lung squamous cell carcinoma one year after RCC surgery. We exploited molecular technology advances to retrospectively investigate the patient's molecular genetic alterations by whole-exome sequencing. The results revealed a 6p21 amplification in VEGFA and TFEB gene acquisition absent in other RCC subtypes. Clear cell, papillary, chromophobe, TFE3-translocation, eosinophilic solid and cystic RCC were excluded. Strong TFEB and Melan-A protein positivity prompted rediagnosis as TFEB/6p21/VEGFA-amplified RCC as per 2022 WHO classification. TMB-L (low tumor mutational load), CCND3 gene acquisition and MRE11A and ATM gene deletion mutations indicated sensitivity to PD-1/PD-L1 inhibitor combinations and the FDA-approved targeted agents Niraparib (Grade C), Olaparib (Grade C), Rucaparib (Grade C) and Talazoparib (Class C). GO (Gene Ontology) and KEGG enrichment analyses revealed major mutations and abnormal CNVs in genes involved in biological processes such as the TGF-β, Hippo, E-cadherin, lysosomal biogenesis and autophagy signaling pathways, biofilm synthesis cell adhesion substance metabolism regulation and others. We compared TFEB/6p21/VEGFA-amplified with TFEB-translocated RCC; significant differences in disease onset age, histological patterns, pathological stages, clinical prognoses, and genetic characteristics were revealed.

CONCLUSION

We clarified the patient's challenging diagnosis and discussed the clinicopathology, immunophenotype, differential diagnosis, and molecular genetic information regarding TFEB/6p21/VEGFA-amplified RCC via exome analysis and a literature review.

Metastatic Translocated Renal Cell Carcinoma in a Kidney Transplant Patient - a Case Report and Review of the Literature

TFEB-altered renal cell carcinomas are rare tumours. Here, we report the exceptional case of such a tumour in the setting of solid organ transplantation and with already metastatic disease at the time of diagnosis. The primary tumour occurred in the native kidney and only focally showed biphasic morphology whereas the metastasis, among others to the transplant kidney, showed nonspecific, albeit different morphology, but both had consistent TFEB translocation. Treatment with the immune checkpoint inhibitor pembrolizumab together with the multi-kinase inhibitor lenvatinib achieved partial response 14 months after diagnosis.

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.

Primary retroperitoneal renal cell carcinoma associated with transcription EB gene fusion

BACKGROUND

Renal cell carcinoma (RCC) with the distinct type of t(6;11) (p21;q12) translocation (transcription factor EB, TFEB) is a rare neoplasm. It is even less when talks about primary retroperitoneal TFEB RCCs. To our knowledge, no previous literature has been reported about this kind of RCCs. In this article, we report a case of primary retroperitoneal renal cell carcinoma associated with transcription EB gene fusion.

METHODS

A 73-year-old male patient presented with a retroperitoneal mass for more than one month.

RESULTS

Pathologically, the mass was soft and colorful, tumor cells showed a biphasic morphology characterized by nests of larger epithelioid cells surrounding intraluminal collections of smaller cells clustered around basement membrane materia. These tumor cells were positive for Pax-8, EMA, TFEB, CK, P504S, Vimentin and CD10 on immunohistochemical stain, and positive for TFEB on fluorescence in situ hybridization assay.

CONCLUSIONS

We reported the first case of primary retroperitoneal renal cell carcinoma associated with transcription EB gene fusion. The pathological feature of the case we reported was very typical. The best treatment at presentation is the total resection. Long-term follow-up study is needed in order to acquire better diagonitic quality and fulfill diagnostic requirements.

Clinical Characteristics of Molecularly Defined Renal Cell Carcinomas

Kidney tumors comprise a broad spectrum of different histopathological entities, with more than 0.4 million newly diagnosed cases each year, mostly in middle-aged and older men. Based on the description of the 2022 World Health Organization (WHO) classification of renal cell carcinoma (RCC), some new categories of tumor types have been added according to their specific molecular typing. However, studies on these types of RCC are still superficial, many types of these RCC currently lack accurate diagnostic standards in the clinic, and treatment protocols are largely consistent with the treatment guidelines for clear cell RCC (ccRCC), which might result in worse treatment outcomes for patients with these types of molecularly defined RCC. In this article, we conduct a narrative review of the literature published in the last 15 years on molecularly defined RCC. The purpose of this review is to summarize the clinical features and the current status of research on the detection and treatment of molecularly defined RCC.

TFEB Rearranged Renal Cell Carcinoma: Pathological and Molecular Characterization of 10 Cases, with Novel Clinical Implications: A Single Center 10-Year Experience

To report our experience with the cases of TFEB rearranged RCC, with particular attention to the clinicopathological, immunohistochemical and molecular features of these tumors and to their predictive markers of response to therapy. We have retrieved the archives of 9749 renal cell carcinomas in the Institute of Urology, Peking University and found 96 rearranged RCCs between 2013 and 2022. Among these renal tumors, ten cases meet the morphologic, immunohistochemical and FISH characterization for TFEB rearranged RCC. The 10 patients' mean and median age is 34.9 and 34 years, respectively (range 23-55 years old), and the male to female ratio is 1:1.5. Macroscopically, these tumors generally have a round shape and clear boundary. They present with variegated, grayish yellow and grayish brown cut surface. The average maximum diameter of the tumor is 8.5 cm and the median 7.7 (ranged from 3.4 to 16) cm. Microscopically, the tumor is surrounded by a thick local discontinuous pseudocapsule. All tumors exhibit two types of cells: voluminous, clear and eosinophilic cytoplasm cells arranged in solid sheet, tubular growth pattern with local cystic changes, and papillary, pseudopapillary and compact nested structures are also seen in a few cases. Non-neoplastic renal tubules are entrapped in the tumor. A biphasic "rosette-like" pattern, psammomatous calcifications, cytoplasmic vacuolization, multinucleated giant cells and rhabdomyoid phenotype can be observed in some tumors. A few tumors may be accompanied by significant pigmentation or hemorrhage and necrosis. The nucleoli are equivalent to the WHO/ISUP grades 2-4. All tumors are moderately to strongly positive for Melan-A, TFEB, Vimentin and SDHB, and negative for CK7, CAIX, CD117, EMA, SMA, Desmin and Actin. CK20 and CK8/18 are weakly positive. In addition, AE1/AE3, P504s, HMB45 and CD10 are weakly moderately positive. TFE3 is moderately expressed in half of the cases. PAX8 can be negative, weakly positive or moderately-strongly positive. The therapy predictive marker for PD-L1 (SP263) is moderately to strongly positive membranous staining in all cases. All ten tumors demonstrate a medium frequency of split TFEB fluorescent signals ranging from 30 to 50% (mean 38%). In two tumors, the coincidence of the TFEB gene copy number gains are observed (3-5 fluorescent signals per neoplastic nuclei). Follow-up is available for all patients, ranging from 4 to 108 months (mean 44.8 and median 43.4 months). All patients are alive, without tumor recurrences or metastases. We described a group of TFEB rearranged RCC identified retrospectively in a large comprehensive Grade III hospital in China. The incidence rate was about 10.4% of rearranged RCCs and 0.1% of all the RCCs that were received in our lab during the ten-year period. The gross morphology, histological features, and immunohistochemistry of TFEB rearranged RCC overlapped with other types of RCC such as TFE3 rearranged RCC, eosinophilic cystic solid RCC, or epithelioid angiomyolipoma, making the differential diagnosis challenging. The diagnosis was based on TFEB fluorescence in situ hybridization. At present, most of the cases reported in the literature have an indolent clinical behavior, and only a small number of reported cases are aggressive. For this small subset of aggressive cases, it is not clear how to plan treatment strategies, or which predictive markers could be used to assess upfront responses to therapies. Between the possible options, immunotherapy currently seems a promising strategy, worthy of further exploration. In conclusion, we described a group of TFEB rearranged RCC identified in a large, comprehensive Grade III hospital in China, in the last 10 years.

Cigarette smoke extract-induced inflammatory response via inhibition of the TFEB-mediated autophagy in NR8383 cells

Objective: Chronic pulmonary inflammation caused by long-term smoking is the core pathology of COPD. Alveolar macrophages (AMs) are involved in the pulmonary inflammation of COPD. The accumulation of damaged materials caused by impaired autophagy triggers inflammatory response in macrophages. As a key transcription regulator, transcription factor EB (TFEB) activates the transcription of target genes related autophagy and lysosome by binding to promoters, whereas it is unclarified for the relationship between inflammatory response induced by cigarette smoke extract (CSE) and TFEB-mediated autophagy. Thus, we investigated the role of TFEB-mediated autophagy in inflammatory response induced by CSE in NR8383 cells, and to explore its potential mechanism. Methods: Based on cell viability and autophagy, cells treated with 20% concentration of CSE for 24 h were selected for further studies. Cells were divided into control group, chloroquine (CQ, the autophagy inhibitor) group, CSE group, CSE + rapamycin (the autophagy inducer) group and CSE + fisetin (the TFEB inducer) group. The levels of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-6 in supernatant were detected by ELISA kits. The protein expressions were tested by western blot. The intensity of fluorescence of Lysosome-associated membrane protein 1 (LAMP1) and TFEB was detected by immunofluorescence. Lyso-Tracker Red staining was applied to detect the lysosome environment. Results: CSE inhibited the cell viability, increased the contents of TNF-α, IL-1β, IL-6, the ratio of LC3II/I, and the level of P62 protein. Besides, CSE decreased the fluorescence intensity of LAMP1 protein and Lyso-Tracker Red staining, as well as the ratio of nucleus/cytosol of TFEB protein. Activating autophagy with rapamycin alleviated CSE-induced inflammatory response. The activation of TFEB via fisetin alleviated CSE-induced autophagy impairment and lysosomal dysfunction, thus alleviated inflammatory response in NR8383 cells. Conclusion: CSE-induced inflammatory response in NR8383 cells, which may be related to the inhibition of TFEB-mediated autophagy.

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.

Papillary renal cell carcinoma: current and controversial issues

PURPOSE OF THE REVIEW

Papillary renal cell carcinoma (pRCC) is the second most frequent renal cancer subtype and represents 15-20% of all RCC. Classification of pRCC is changing because novel tumour entities have been discovered in the last years. In this review, we summarise recent studies relevant for the understanding of the molecular complexity and the broader differential diagnosis of pRCC.

RECENT FINDINGS

It has been 25 years ago, that pRCC was morphologically subdivided into type 1 and type 2. Recently described tumour entities in the 2022 WHO classification challenged this concept and allow a new view on the molecular background in pRCC. Biphasic hyalinizing psammomatous RCC and papillary renal neoplasm with reversed polarity are emerging tumour entities derived from the new concept of molecularly defined RCC subtypes. Immune checkpoint inhibition and tyrosine kinase inhibitors have been introduced as the new backbone in the first-line treatment of advanced pRCCs. To identify novel targeted treatments for patients with pRCC it is crucial to investigate the specific molecular background of pRCC considering emerging pRCC subtypes.

SUMMARY

In the future, a deeper understanding of the correlation between molecular aberrations and new pRCC subtypes may improve the classification of pRCC patients and could reveal potential predictive biomarkers for each subgroup.

Comprehensive study of 9 novel cases of TFEB-amplified renal cell carcinoma: an aggressive tumor with frequent PDL1 expression

BACKGROUND & OBJECTIVES

First described in 2014, renal cell carcinoma (RCC) with TFEB amplification (6p21) is a rare molecular subgroup whose diagnosis is challenging. The prognosis and therapeutic implications remain unclear.

METHODS

We report here the clinical, histological, immunohistochemical and genetic features of 9 novel cases. The pathological and immunohistochemical features were centrally reviewed by expert uropathologists. Fluorescence in situ hybridization (FISH) confirmed the diagnosis and comparative genomic hybridization (CGH) was performed to determine quantitative genomic alterations. We also performed an exhaustive review of the literature and compiled our data.

RESULTS

TFEB-amplified RCC were locally advanced with initial lymph node involvement in one case and liver metastasis in another case. They were high-grade eosinophilic tumors with papillary/pseudopapillary architecture, frequent positivity for melanocytic markers and frequent PDL1 expression. FISH demonstrated high-level TFEB amplification in 6 cases. One case showed concomitant TFEB translocation. CGH analysis identified complex alterations with frequent losses of 1p, 2q, 3p, 6p, and frequent 6p and 8q gains. VEGFA co-amplification was identified in all cases with a lower level than TFEB. The prognosis was poor with five patients having lymph node or distant metastases.

CONCLUSION

TFEB-amplified RCC is a rare molecular subgroup with variable morphology whose diagnosis is confirmed by FISH analysis. The complex alterations identified by CGH are consistent with an aggressive clinical behavior. The co-amplification of VEGFA and the expression of PDL1 could suggest a potential benefit from antiangiogenics and targeted immunotherapy in combination for these aggressive tumors.

Eosinophilic solid and cystic renal cell carcinoma and renal cell carcinomas with TFEB alterations: a comparative study

AIMS

Eosinophilic solid and cystic renal cell carcinoma (ESC RCC) is a recently described renal tumour entity with frequent CK20 positivity, commonly harbouring TSC mutations. In contrast, frequency of CK20 expression and presence of TSC mutations are unclear in TFEB-amplified RCC and TFEB-translocated RCC, which frequently express Melan A. Herein, we provide a comparative analysis of 6 ESC RCC with 4 TFEB-amplified/translocated RCC.

METHODS AND RESULTS

We assessed the frequency of CK20 and Melan A expression by immunohistochemistry, and of TSC mutations by next generation sequencing. TFEB alterations were confirmed by fluorescence in situ hybridization (FISH). All tumours showed voluminous eosinophilic cells with granular cytoplasm, prominent nucleoli, and most showed admixture of solid and cystic areas. CK20 expression was found in all 6 ESC RCC and in all RCCs with TFEB alterations. Melan A positivity was identified in 5/6 ESC RCC and 4/4 RCC with TFEB alterations. We found TSC mutations in 2 ESC RCCs, including in one case also harbouring a CIC fusion, and identified a TSC mutation in one TFEB-amplified RCC.

CONCLUSIONS

ESC RCC represents an emerging renal tumour entity with some histological, immunohistochemical and molecular overlap to TFEB-amplified/translocated RCC. FISH for TFEB aids in this differential diagnosis in challenging cases.

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.

Heat-induced antigen retrieval in fluorescence in situ hybridization: An effective approach enhancing signal intensity in poor-quality FFPE sections

Fluorescence in situ hybridization (FISH) serves as an ancillary tool for assessing chromosomal abnormalities and is important in differential diagnoses and treatment decisions. In clinical practice, pathologists encounter unsatisfactory formalin-fixed paraffin-embedded (FFPE) sections exhibiting weak fluorescence signals, mostly due to inappropriate tissue processing or preservation, leading to interpretation difficulties. For the present study, FFPE samples for which conventional FISH failed were collected. Instead of a pretreatment step using a commercial kit, heat-induced antigen retrieval (HIAR) was introduced using either citrate buffer or Tris-EDTA buffer, while the subsequent experimental workflow remained unchanged. After HIAR-assisted FISH, the hybridization efficiency and signal intensity were markedly enhanced and no difference in signal adequacy was observed when comparing the effect of the two AR solutions. The present study demonstrated that HIAR is a reliable tool for FISH, particularly for poor-quality FFPE sections yielding weak or no fluorescence signals in the conventional analysis.

t(6; 11) renal cell carcinoma. A case report successfully diagnosed by using fluorescence in situ hybridization

INTRODUCTION

Definitive diagnosis of translocation renal cell carcinoma is challenging. We herein experienced a case of translocation(6;11) renal cell carcinoma, successfully diagnosed by using fluorescence in situ hybridization.

CASE PRESENTATION

During the follow-up of a 21-year-old man with Crohn's disease, computed tomography revealed a 40-mm mass in the right kidney. Since imaging could not exclude malignancy, needle biopsy was performed. The histological diagnosis from the biopsy specimen was renal cell carcinoma, but histological typing had not been done adequately. A laparoscopic partial nephrectomy was then performed. Transcription factor EB immunoreactivity was positive, transcription factor EB rearrangement was shown by break apart and fusion fluorescence in situ hybridization. As a result, a definitive diagnosis of t(6; 11) renal cell carcinoma was made. There has been no recurrence for 5 years.

CONCLUSION

Transcription factor EB immunohistochemistry and fluorescence in situ hybridization are useful diagnostic tools for renal tumors of young generation.

Pathology and systemic therapy of non-clear cell renal cell carcinoma: an overview

Introduction: Non-clear cell renal cell carcinoma (nccRCC) represents a highly heterogenous group of kidney cancer entities. As most clinical trials predominantly include patients with clear cell RCC (ccRCC), nccRCC treatment guidelines are mainly extrapolated from recommendations in ccRCC. Here, we review and elucidate current data on the pathologic classification and treatment of nccRCC.Areas covered: This article gives an overview of the WHO classification of RCC, showing the histological diversity of nccRCC and focusing particularly on entities first characterized since 2016, their specific molecular behavior and their role as indicators for hereditary cancer syndromes. In this context, we discuss the available data on nccRCC treatment oprtions such as tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors, cytotoxic chemotherapy, and immune checkpoint inhibitors.Expert opinion: Although nccRCCs are relatively uncommon, entities of this type account for a subgroup of up to 20-25% of all RCCs. Advances in histopathology and molecular genetics, together with evidence gained from retrospective and prospective clinical data, have improved understanding of these tumors in recent years. Nevertheless, selective trials of current and novel therapies including new targeted agents in patients with nccRCC are urgently needed to further improve treatment guidelines.

Non-clear cell renal carcinomas: Review of new molecular insights and recent clinical data

Non-clear cell renal cell carcinomas (nccRCC) represent a highly heterogeneous group of kidney tumors, consisting of the following subtypes: papillary carcinomas, chromophobe renal cell carcinoma, so-called unclassified carcinomas or aggressive uncommon carcinomas such as Bellini carcinoma, renal cell carcinoma (RCC) with ALK rearrangement or fumarate hydratase-deficient RCC. Although non-clear cell cancers account for only 15 to 30% of renal tumors, they are often misclassified and accurate diagnosis continues to be an issue in clinical practice. Current therapeutic strategy of metastatic nccRCC is based primarily on guidelines established for clear cell tumors, the most common subtype, however this approach remains poorly defined. To date, published clinical trials for all histological nccRCC subtypes have been collectively characterized into one group, in contrast to clear cell RCC, and given the small numbers of cases, the interpretation of study results continues to be challenging. This review summarizes the available literature for each nccRCC subtype and highlights the lack of supportive evidence from prospective clinical trials and retrospective studies. Future trials should evaluate treatment approaches which focus on a specific histological subtype and progress in treating nccRCC will be contingent on understanding the unique biology of their individual histologies.

[Histological subtypes of renal cell carcinoma : Overview and new developments]

BACKGROUND

The classification of renal cell carcinoma (RCC) has changed remarkably in recent years.

OBJECTIVES

This is a short overview of the classification of RCC, focusing on new developments.

MATERIALS AND METHODS

A literature search was performed resulting in an overview of the classification of RCC. Emerging entities were discussed in detail.

RESULTS

Apart from the RCC subtypes in the WHO classification of 2016, several emerging entities came up over the last few years that are characterized by typical morphology, immunophenotype, and especially specific genetic alterations.

CONCLUSION

Precise classification of RCC is the key to better prognostic assessment with potential tumor-specific therapy and plays an important role in the recognition of possible association with hereditary tumor syndromes.

Towards a new WHO classification of renal cell tumor: what the clinician needs to know-a narrative review

In 1952, renal cell carcinomas had been divided into 2 categories—clear cell or granular cell—depending upon their cytoplasmic staining characteristics. In the following years, the inventory of renal epithelial tumors has expanded by the addition of tumors named by their architectural pattern (i.e., papillary RCC, tubulocystic RCC), anatomic location (i.e., collecting duct carcinoma, renal medullary carcinoma), associated diseases (i.e., acquired cystic disease-associated RCCs). With the extensive application of molecular diagnostic techniques, it becomes possible to detect genetic distinctions between various types of renal neoplasm and discover new entities, otherwise misdiagnosed or diagnosed as unclassified RCC. Some tumors such as ALK rearrangement-associated RCC, MiT family translocation renal carcinomas, SDH-deficient renal cancer or FH-deficient RCC, are defined by their molecular characteristics. The most recent World Health Organization (WHO) classification of renal neoplasms account for more than 50 entities and provisional entities. New entities might be included in the upcoming WHO classification. The aim of this review is to summarise and discuss the newly acquired data and evidence on the clinical, pathological, molecular features and on the prognosis of new RCC entities, which will hopefully increase the awareness and the acceptance of these entities among clinicians and improve prognostication for individual patients.

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.

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.

[Characterization of different renal cell carcinoma entities]

BACKGROUND

In recent years, the characterization of different renal cell carcinoma entities has significantly improved, in particular due to molecular typing.

OBJECTIVES

Classical, accepted and emerging renal cell carcinoma entities are described.

MATERIALS AND METHODS

A literature search was performed, followed by evaluation and description of the literature focusing on different renal cell carcinoma entities.

RESULTS

Classical renal cell carcinoma entities such as clear cell carcinoma, papillary renal cell carcinoma and chromophobe renal cell carcinoma have been expanded in particular by molecular techniques to include, for example, translocation carcinoma or carcinoma with mutations in genes of the mitochondrial energy metabolism. Some rare entities have been accepted by the World Health Organization (WHO) classification, while some are considered as emerging entities.

CONCLUSIONS

A range of newly accepted and emerging renal cell carcinoma entities have been introduced in the 2016 WHO classification. A precise and correct diagnosis is of major importance regarding the prognostic assessment, potential new therapeutic strategies and possible hereditary associations.

MiT family translocation renal cell carcinomas: A 15th anniversary update

Microphthalmia (MiT) family translocation renal cell carcinomas (RCCs) are a heterogeneous category of renal tumors which all express MiT transcription factors, typically from chromosomal translocation and rarely from gene amplification. This tumor family has two major subtypes [i.e., Xp11 translocation RCC and t(6;11) RCC] and several related neoplasms (i.e., TFEB amplification RCC and melanotic Xp11 translocation renal cancers). Increased understanding of the clinical, pathological, molecular and prognostic heterogeneity of these tumors, since their official recognition in 2004, provides the opportunity to identify prognostic biomarkers and to understand the reasons for tumor aggression. We will review the literature from the past 15 years and highlight the need for a greater understanding of the molecular mechanisms underpinning heterogeneous tumor behavior.