Xp11 Translocation Renal Cell Carcinoma Research Articles

A genetic basis for sex differences in Xp11 translocation renal cell carcinoma

Xp11 translocation renal cell carcinoma (tRCC) is a rare, female-predominant cancer driven by a fusion between the transcription factor binding to IGHM enhancer 3 (TFE3) gene on chromosome Xp11.2 and a partner gene on either chromosome X (chrX) or an autosome. It remains unknown what types of rearrangements underlie TFE3 fusions, whether fusions can arise from both the active (chrXa) and inactive X (chrXi) chromosomes, and whether TFE3 fusions from chrXi translocations account for the female predominance of tRCC. To address these questions, we performed haplotype-specific analyses of chrX rearrangements in tRCC whole genomes. We show that TFE3 fusions universally arise as reciprocal translocations and that oncogenic TFE3 fusions can arise from chrXi:autosomal translocations. Female-specific chrXi:autosomal translocations result in a 2:1 female-to-male ratio of TFE3 fusions involving autosomal partner genes and account for the female predominance of tRCC. Our results highlight how X chromosome genetics constrains somatic chrX alterations and underlies cancer sex differences.

The GATOR2 complex maintains lysosomal-autophagic function by inhibiting the protein degradation of MiT/TFEs

Lysosomes are central to metabolic homeostasis. The microphthalmia bHLH-LZ transcription factors (MiT/TFEs) family members MITF, TFEB, and TFE3 promote the transcription of lysosomal and autophagic genes and are often deregulated in cancer. Here, we show that the GATOR2 complex, an activator of the metabolic regulator TORC1, maintains lysosomal function by protecting MiT/TFEs from proteasomal degradation independent of TORC1, GATOR1, and the RAG GTPase. We determine that in GATOR2 knockout HeLa cells, members of the MiT/TFEs family are ubiquitylated by a trio of E3 ligases and are degraded, resulting in lysosome dysfunction. Additionally, we demonstrate that GATOR2 protects MiT/TFE proteins in pancreatic ductal adenocarcinoma and Xp11 translocation renal cell carcinoma, two cancers that are driven by MiT/TFE hyperactivation. In summary, we find that the GATOR2 complex has independent roles in TORC1 regulation and MiT/TFE protein protection and thus is central to coordinating cellular metabolism with control of the lysosomal-autophagic system.

Identification of Key Differentially Expressed mRNAs, miRNAs, lncRNAs, and circRNAs for Xp11 Translocation Renal Cell Carcinoma (RCC) Based on Whole-Transcriptome Sequencing

We carried out whole transcriptome sequencing (WTS) on the tumor and the matching adjacent normal tissues from five patients having Xp11 translocation renal cell carcinoma (RCC). This was performed in terms of obtaining more understanding of the genomic panorama and molecular basis of this cancer. To examine gene-regulatory networks in XP11 translocation RCC, variance expression analysis was carried out, followed by functional enrichment analysis. Gene Expression Omnibus (GEO) of Xp11 translocation RCC data was used to validate the results. As per inclusion criteria, a total of 1886 differentially expressed mRNAs (DEmRNAs), 56 differentially expressed miRNAs (DEmiRNAs), 223 differentially expressed lncRNAs (DElncRNAs), and 1764 differentially expressed circRNAs (DEcircRNAs) were found. KEGG enrichment study of DEmiRNA, DElncRNA, and DEcircRNA target genes identified the function of protein processing in the endoplasmic reticulum, lysosome, and neutrophil-mediated immunity. Three subnetwork modules integrated from the PPI network also revealed the genes involved in protein processing in the endoplasmic reticulum, lysosome, and protein degradation processes, which may regulate the Xp11 translocation RCC process. The ceRNA complex network was created by Cytoscape, which included three upregulated circRNAs, five upregulated lncRNAs, 24 upregulated mRNAs, and two downregulated miRNAs (hsa-let-7d-5p and hsa-miR-433-3p). The genes as a prominent component of the complex ceRNA network may be key factors in the pathogenesis of Xp11 translocation RCC. Our findings clarified the genomic and transcriptional complexity of Xp11 translocation RCC while also pointing to possible new targets for Xp11 translocation RCC characterization.

PEComa-like Neoplasms Characterized by ASPSCR1-TFE3 Fusion: Another Face of TFE3-related Mesenchymal Neoplasia.

Identical TFE3-related gene fusions may be found in renal cell carcinoma and mesenchymal neoplasms such as alveolar soft part sarcoma and TFE3-rearranged perivascular epithelioid cell tumor (PEComa). Among mesenchymal neoplasms, the ASPSCR1-TFE3 gene fusion has previously been described only in alveolar soft part sarcoma. We report 3 unusual mesenchymal neoplasms harboring the ASPSCR1-TFE3 gene fusion, the morphologic phenotype of which more closely matches PEComa rather than alveolar soft part sarcoma. All 3 neoplasms occurred in females ranging in age from 18 to 34 years and were located in the viscera (kidney, bladder, and uterus). All 3 contained nests of epithelioid cells bounded by fibrovascular septa. However, all were associated with hyalinized stroma, tight nested architecture, mixed spindle cell and epithelioid pattern, clear cytoplasm, and lacked significant discohesion. Overall, morphologic features closely resembled PEComa, being distinct from the typical alveolar soft part sarcoma phenotype. While none of the neoplasms labeled for HMB45, cytokeratin, or PAX8 all showed positivity for TFE3 and cathepsin K, and all except 1 were positive for smooth muscle actin. One patient developed a liver metastasis 7 years after nephrectomy. These cases bridge the gap between 2 TFE3-rearranged neoplasms, specifically alveolar soft part sarcoma and Xp11 translocation PEComa, highlighting the relatedness and overlap among Xp11 translocation neoplasms. While most TFE3-rearranged neoplasms can be confidently placed into a specific diagnostic category such as alveolar soft part sarcoma, PEComa, or Xp11 translocation renal cell carcinoma, occasional cases have overlapping features, highlighting the potential role that the cell of origin and the specific gene fusion play in the phenotype of these neoplasms.

Translocation carcinomas of the kidney.

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

RBM10‐TFE3 fusions: A FISH‐concealed anomaly in adult renal cell carcinomas displaying a variety of morphological and genomic features: Comprehensive study of six novel cases

The accurate diagnosis of Xp11-translocation renal cell carcinoma (RCC) in adults is challenging. TFE3 (located on chromosome X) fuses with a partner gene generally located on another chromosome. In rare cases TFE3 may fuse with a neighboring gene: RBM10. Because TFE3 false-positive immunostaining is a common pitfall in many laboratories, demonstration of the chromosomal rearrangement is required in order to ascertain the diagnosis. Fluorescence in situ hybridization (FISH)-that has been considered as the gold standard method-reaches its limits for detecting small Xp11 paracentric inversions. We performed a comprehensive clinical, histological and genomic study of six novel cases of RCC with RBM10-TFE3 fusion. Using FISH, TFE3 rearrangement was equivocal in one case and negative in others. RBM10-TFE3 fusion was discovered using targeted RNA sequencing (RNASeq). As all the previously reported cases (mean age: 50), the six patients were adults (mean age: 42), suggesting an epidemiologic difference between RBM10-TFE3 RCC and tumors harboring some other partner genes, such as ASPSCR1 that rather occur in children. Array-comparative genomic hybridization showed several alterations, notably a gain of 17q in four cases with papillary features and loss of 3p in one case with clear cells. Our study demonstrates that, though rare among adult cases of RCC, RBM10-TFE3 fusion is not exceptional and warrants appropriate molecular detection. Notably, it would be worthy to systemically investigate by RNASeq challenging RCC with type-2 papillary features and 17q gain.

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

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

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.

BAP1-Mutated Clear Cell Renal Cell Carcinoma.

While aberrations in the VHL gene and chromosome 3p resulting in clear cell renal cell carcinoma (CCRCC) are well established, we know that additional mutations in chromatin remodeling genes PBRM1, SETD2, and BRCA1-associated protein 1 (BAP1) contribute to pathogenesis in some cases. Given the known aggressive clinical behavior of BAP1-mutated CCRCC, we sought to define the pathologic phenotype of BAP1-mutated CCRCC. We identified 14 cases of molecularly proven BAP1-mutated CCRCC and investigated their clinicopathologic features. BAP1-mutated CCRCC frequently showed papillary, tubulopapillary, or expanded nested architecture; demonstrated granular to diffusely eosinophilic cytoplasm with prominent eosinophilic globules; and contained high-grade nuclei. This morphology demonstrates significant overlap with Xp11 translocation renal cell carcinoma (RCC). Immunohistochemistry notably demonstrates loss of BAP1 expression in almost all tumors, in addition to strong p504S expression. A conventional CCRCC component was frequently present adjacent to the characteristic BAP1 areas and showed retained BAP1 expression and only patchy p504S. Approximately two-thirds of BAP1-mutated CCRCCs were stage pT3, renal vein invasion was common, and 50% developed metastases. Herein, we describe the histologic and immunohistochemical findings in BAP1-mutated CCRCC, which has important implications for utilization of molecular testing, prognosis, future therapeutics, and distinction from other RCC subtypes such as Xp11 translocation RCC.

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

AimsXp11 translocation renal cell carcinoma (RCC) is a distinctive subtype of RCC with TFE3 (Transcription Factor Binding to IGHM Enhancer 3) gene rearrangement. The gross features in most Xp11 translocation...

Malignant melanotic Xp11 neoplasms exhibit a clinicopathologic spectrum and gene expression profiling akin to alveolar soft part sarcoma: a proposal for reclassification.

The classification of the distinct group of mesenchymal neoplasms, first described as 'Xp11 translocation perivascular epithelioid cell tumor (PEComa)' and for which the term 'melanotic Xp11 neoplasm' or 'Xp11 neoplasm with melanocytic differentiation' has recently been proposed, remains challenging and controversial. We collected 27 melanotic Xp11 neoplasms, the largest series to date, for a comprehensive evaluation. Fourteen of the cases, together with eight alveolar soft part sarcomas (ASPS), nine conventional PEComas and a control group of seven normal tissues were submitted to RNA sequencing. Follow-up available in 22 patients showed 5-year overall survival and 5-year disease-free survival of 47.6 and 35.7%, respectively, which were similar to ASPS and significantly worse than conventional PEComa. Univariate analysis of location (occurring in the kidney versus not kidney), infiltrative growth pattern, nuclear pleomorphism, mitotic activity ≥2/50 high-power fields (HPF), necrosis and lymphovascular invasion were found to be associated with overall survival and/or disease-free survival. Multivariate analysis identified that location was the only factor found to independently correlate with disease-free survival. More importantly, RNA sequencing-based clustering analysis segregated melanotic Xp11 neoplasm and ASPS from other tumors, including conventional PEComa and Xp11 translocation renal cell carcinoma, and formed a compact cluster representative of the largely similar expression signature. Here we clearly define the true biologic nature of melanotic Xp11 neoplasms which are distinctive malignant mesenchymal tumors, rather than simply PEComa variants with occasionally unpredictable behavior. Meanwhile, melanotic Xp11 neoplasm and ASPS more likely represent phenotypic variants of the same entity, which is distinct from conventional PEComa and Xp11 translocation renal cell carcinoma. Based on these important findings, melanotic Xp11 neoplasm might be reclassified into a distinctive entity together with ASPS, independent from PEComa, in future revisions of the current WHO categories of tumors of soft tissue and bone for the improved reclassification. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

PD-L1 expression and infiltration by CD4+ and FoxP3+ T cells are increased in Xp11 translocation renal cell carcinoma and indicate poor prognosis.

Interaction between programmed death-1 ligand (PD-L1) and its receptor programmed death 1 (PD-1) on T cells inactivates antitumour immune responses. PD-L1 expression has been associated with poor prognosis in renal cell carcinoma (RCC) and predicts adverse outcome. This study was designed to evaluate the impact of PD-L1 expression and the immune microenvironment on the clinical outcome in Xp11 translocation renal cell carcinoma (TRCC) and, therefore, their potential relevance as prognostic biomarkers. The present retrospective analysis investigated expression of PD-L1 and immune cells CD8, CD4, CD3, forkhead box protein 3 (FoxP3) and PD-1 in TRCC compared to other types of RCC. FFPE specimens were collected between 2011 and 2017 from 311 patients who underwent nephrectomy at our institution for RCC. Specimens were immunostained for PD-L1, CD8, CD4, CD3, FoxP3 and PD-1, and an outcome analysis was conducted. PD-L1 expression rate was highest in TRCC (68%, 16 of 25), followed by mucinous tubular and spindle cell RCC and collecting duct carcinoma (33%, one of three), papillary RCC (27%, seven of 26), clear cell RCC (16%, 29 of 233), chromophobe RCC (11%, two of 18) and multilocular cystic RCC (0%, none of three). In TRCC, PD-L1 expression was associated with poor recurrence-free survival (RFS) (P=0.041). The CD4high and FoxP3high groups showed a significantly shorter RFS (P=0.05 and P=0.031, respectively) compared to CD4low and FOXPlow groups. PD-L1 expression was higher in TRCC than in other types of RCC. High PD-L1 tumour cell expression and tumour infiltration by CD4+ and FoxP3+ immune cells were associated with poor RFS in TRCC.

Comparative Clinicopathologic Characteristics and Outcomes of Paediatric and Adult Xp11 Translocation Renal Cell Carcinomas: a Retrospective Multicentre Study in China

This study aimed to compare the clinicopathologic features and prognosis in patients with Xp11 translocation renal cell carcinomas (RCCs). In total, 8083 RCCs were screened at five centres from January 2007 to December 2018, including 8001 adults (≥18 years) and 82 children (<18 years). Finally, 73 adults and 17 children were identified as Xp11 translocation RCCs, accounting for 1.1% (90 of 8083) of the RCCs. However, 4 children and 1 adult were excluded because of loss to follow-up when performing the survival analysis. The proportion of paediatric and adult Xp11 translocation RCCs was 20.7% (17 of 82) and 0.9% (73 of 8001) of RCCs, respectively, and the incidence in children and adults was significantly different (P < 0.01). Lymph node positivity (LN+) most commonly occurred in children (58.8%) compared with adults (28.8%; P = 0.02), but children with LN+ showed significantly higher five-year overall survival and progression-free rates (OS: 75.0%; PFS: 64.8%) than adult patients (OS: 40.3%; PFS: 0%) (log-rank PPFS < 0.01; POS = 0.04). Multivariable analysis indicated that local lymph node metastasis was associated with both PFS (HR = 0.10; 95% CI 0.02–0.51; P = 0.01) and OS (HR = 0.11; 95% CI 0.01–0.98; P = 0.04) in adults. Adult patients with LN+ may indicate a worse prognosis than paediatric patients.

Cytopathology of Xp11 translocation renal cell carcinoma: a report of 5 cases

Xp11.2 translocation-associated RCC (Xp11RCC) defined by molecular alterations involving TFE3 genetic rearrangements constitutes a large percentage of primary renal neoplasms in children, but less than 4% of adult cases. Fewer than 10 single case reports constitute the English cytopathology literature regarding this neoplasm. Our objective is to describe and illustrate the cytopathology of this uncommon renal neoplasm from a series of 5 cases using cytologic imprints, effusion specimens, and fine-needle aspiration (FNA) cytology. Review was made of our cytopathology and surgical pathology databases. FNA biopsy smears and imprint smears were performed using a standard technique. Effusion samples were processed using liquid-based slides. Five cytologic specimens from 4 patients with histopathologically confirmed Xp11RCC were identified (mean age: 36 years) over a period of 7 years. All cases contained large cells with voluminous amounts of vacuolated cytoplasm arranged in non-descript clusters and as single forms. A "tigroid" pattern consisting of linear strips of detached cytoplasm was seen in both imprint smear cases and the single FNA case. Psammomatous calcifications, true papillary structures, and hyaline globules were absent in all cases. Four examples were diagnosed as Xp11RCC, but 3 represented metastatic disease, and 1 was diagnosed using both cytology and core needle tissue histopathology. The remaining case was diagnosed nonspecifically as a clear cell malignant neoplasm. The cytopathologic features of Xp1RCC are relatively nonspecific, and overlap with other renal cell carcinoma subtypes. A definitive diagnosis is only possible with ancillary immunohistochemistry with or without additional TFE3 fluorescence in situ hybridization.

Xp11 translocation renal cell carcinoma with vertebral metastasis presenting with low back pain and sciatica.

Xp11 translocation renal cell carcinoma with vertebral metastasis presenting with low back pain and sciatica.

A Rare Partner of TFE3 in the Xp11 Translocation Renal Cell Carcinoma: Clinicopathological Analyses and Detection of MED15-TFE3 Fusion.

Xp11 translocation renal cell carcinoma (RCC), a member of the microphthalmia-associated transcription factor (MiTF) family, is a rare renal tumor characterized by different translocations involving the TFE3 gene. Here, we reported a case of Xp11 translocation RCC with a rare MED15-TFE3 gene fusion by RNA sequencing. Morphologically, the tumor cells were arranged in a solid and small nest pattern. The cytoplasm was voluminous, flocculent eosinophilic, and vacuolated. The nuclei were round or polygon with fine granular chromatin, and the nucleoli were unconspicuous. Psammoma bodies were observed in mesenchyma. Immunohistochemically, the tumor cells were diffuse moderately or strongly positive for CD10, P504S, vimentin, PAX8, RCC, AE1/AE3, and SDHB and focally positive for CK7 and CA IX while negative for cathepsin K, HMB45, Melan-A, Ksp-cadherin, and CD117. The Ki67 proliferation index was approximately 3%. However, TFE3 labeling showed an uncertainly weak nuclear staining and been considered negative. Fluorescence in situ hybridization (FISH) demonstrated a positive result that splits signals with a distance of > 2 signal diameters. Subsequently, RNA sequencing confirmed a fusion of MED15 gene exon 11 on chromosome 22 with TFE3 gene exon 6 in the tumor. The patient was alive with no evidence of recurrence. Our report contributes to the understanding on MED15-TFE3 RCC.

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

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

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.

MiT Family Translocation Renal Cell Carcinoma: from the Early Descriptions to the Current Knowledge.

The new category of MiT family translocation renal cell carcinoma has been included into the World Health Organization (WHO) classification in 2016. The MiT family translocation renal cell carcinoma comprises Xp11 translocation renal cell carcinoma harboring TFE3 gene fusions and t(6;11) renal cell carcinoma harboring TFEB gene fusion. At the beginning, they were recognized in childhood; nevertheless, it has been demonstrated that these neoplasms can occur in adults as well. In the nineties, among Xp11 renal cell carcinoma, ASPL, PRCC, and SFPQ (PSF) were the first genes recognized as partners in TFE3 rearrangement. Recently, many other genes have been identified, and a wide spectrum of morphologies has been described. For this reason, the diagnosis may be challenging based on the histology, and the differential diagnosis includes the most common renal cell neoplasms and pure epithelioid PEComa/epithelioid angiomyolipoma of the kidney. During the last decades, many efforts have been made to identify immunohistochemical markers to reach the right diagnosis. To date, staining for PAX8, cathepsin K, and melanogenesis markers are the most useful identifiers. However, the diagnosis requires the demonstration of the chromosomal rearrangement, and fluorescent in situ hybridization (FISH) is considered the gold standard. The outcome of Xp11 translocation renal cell carcinoma is highly variable, with some patients surviving decades with indolent disease and others dying rapidly of progressive disease. Despite most instances of t(6;11) renal cell carcinoma having an indolent clinical course, a few published cases demonstrate aggressive behavior. Recently, renal cell carcinomas with TFEB amplification have been described in connection with t(6;11) renal cell carcinoma. Those tumors appear to be associated with a more aggressive clinical course. For the aggressive cases of MiT family translocation carcinoma, the optimal therapy remains to be determined; however, new target therapies seem to be promising, and the search for predictive markers is mandatory.

RNA sequencing of Xp11 translocation-associated cancers reveals novel gene fusions and distinctive clinicopathologic correlations

Both Xp11 translocation renal cell carcinomas and the corresponding mesenchymal neoplasms are characterized by a variety of gene fusions involving TFE3. It has been known that tumors with different gene fusions may have different clinicopathologic features; however, further in-depth investigations of subtyping Xp11 translocation-associated cancers are needed in order to explore more meaningful clinicopathologic correlations. A total of 22 unusual cases of Xp11 translocation-associated cancers were selected for the current study; 20 cases were further analyzed by RNA sequencing to explore their TFE3 gene fusion partners. RNA sequencing identified 17 of 20 cases (85%) with TFE3-associated gene fusions, including 4 ASPSCR1/ASPL-TFE3, 3 PRCC-TFE3, 3 SFPQ/PSF-TFE3, 1 NONO-TFE3, 4 MED15-TFE3, 1 MATR3-TFE3, and 1 FUBP1-TFE3. The results have been verified by fusion fluorescence in situ hybridization (FISH) assays or reverse transcriptase polymerase chain reaction (RT-PCR). The remaining 2 cases with specific pathologic features highly suggestive of MED15-TFE3 renal cell carcinoma were identified by fusion FISH assay. We provide the detailed morphologic and immunophenotypic description of the MED15-TFE3 renal cell carcinomas, which frequently demonstrate extensively cystic architecture, similar to multilocular cystic renal neoplasm of low malignant potential, and expressed cathepsin K and melanotic biomarker Melan A. This is the first time to correlate the MED15-TFE3 renal cell carcinoma with specific clinicopathologic features. We also report the first case of the corresponding mesenchymal neoplasm with MED15-TFE3 gene fusion. Additional novel TFE3 gene fusion partners, MATR3 and FUBP1, were identified. Cases with ASPSCR1-TFE3, SFPQ-TFE3, PRCC-TFE3, and NONO-TFE3 gene fusion showed a wide variability in morphologic features, including invasive tubulopapillary pattern simulating collecting duct carcinoma, extensive calcification and ossification, and overlapping and high columnar cells with nuclear grooves mimicking tall cell variant of papillary thyroid carcinoma. Furthermore, we respectively evaluated the ability of TFE3 immunohistochemistry, TFE3 FISH, RT-PCR, and RNA sequencing to subclassify Xp11 translocation-associated cancers. In summary, our study expands the list of TFE3 gene fusion partners and the clinicopathologic features of Xp11 translocation-associated cancers, and highlights the importance of subtyping Xp11 translocation-associated cancers combining morphology, immunohistochemistry, and multiple molecular techniques.