Transcription factor E3 (TFE3) belongs to a basic helix-loop-helix family, and is involved in the biology of osteoclasts, melanocytes and their malignancies. We previously reported the metabolic effects of TFE3 on insulin in the liver and skeletal muscles in animal models. In the present study, we explored a novel role for TFE3 in a skeletal muscle cell line. When TFE3 was overexpressed in C2C12 myoblasts by adenovirus before induction of differentiation, myogenic differentiation of C2C12 cells was significantly inhibited. Adenovirus-mediated TFE3 overexpression also suppressed the gene expression of muscle regulatory factors (MRFs), such as MyoD and myogenin, during C2C12 differentiation. In contrast, knockdown of TFE3 using adenovirus encoding short-hairpin RNAi specific for TFE3 dramatically promoted myoblast differentiation associated with significantly increased expression of MRFs. Consistent with these findings, promoter analyses via luciferase reporter assay and electrophoretic mobility shift assay suggested that TFE3 negatively regulated myogenin promoter activity by direct binding to an E-box, E2, in the myogenin promoter. These findings indicated that TFE3 has a regulatory role in myoblast differentiation, and that transcriptional suppression of myogenin expression may be part of the mechanism of action.

DNase I-hypersensitive sites in cellular chromatin are usually believed to be nucleosome-free regions generated by transcription factor binding. Using a cell-free system we show that hypersensitivity does not simply correlate with the number of DNA-bound proteins. Specifically, the leucine zipper containing basic helix-loop-helix protein TFE3 was sufficient to induce a DNase I-hypersensitive site at the immunoglobulin heavy chain micro enhancer in vitro. TFE3 enhanced binding of an ETS protein PU.1 to the enhancer. However, PU.1 binding erased the DNase I-hypersensitive site without abolishing TFE3 binding. Furthermore, TFE3 binding enhanced transcription in the presence and absence of a hypersensitive site, whereas endonuclease accessibility correlated strictly with DNase I hypersensitivity. We infer that chromatin constraints for transcription and nuclease sensitivity can differ.

Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion has been recently identified. Herein is presented a case of RCC with Xp11.2 translocations/TFE3 gene fusions with unusual histological findings. A 68-year-old Japanese woman was incidentally found to have a renal mass on CT. Histological examination showed clear cell neoplasm with alveolar and papillary growth patterns. The nuclear atypia corresponded to Fuhrman grade 3. Additionally, smooth muscle stroma was observed and abnormal vessels showing a heterogeniety in thickness were also identified. On immunohistochemistry, neoplastic cells were diffusely positive for transcription factor E3 (TFE3) and Melan A, and focally positive for CD10 and RCC marker. The smooth muscle stroma was positive for alpha-smooth muscle actin and h-caldesmon, but reverse transcription-polymerase chain reaction of the tumor using frozen material could not detect any previously reported chimeric transcripts including ASPL-TFE3, PRCC-TFE3, CLTC-TFE3, PSF-TFE3 or NoNo-TFE3. G-band karyotype was unsuccessful. Pathologists should pay attention to the afore-described unusual stromal reaction of adult-onset RCC associated with Xp11.2 translocations/TFE3 gene fusions.

Xp11.2-translocation renal carcinoma (TRCC) is suspected when a renal carcinoma occurs in young patients, patients with a prior history of exposure to chemotherapy and when the neoplasm has morphological features suggestive of that entity. We retrieved 20 renal tumours (from 17,500 archival cases) of which morphology arose suspicion for TRCC. In nine cases, TFE3 translocation was confirmed by fluorescence in situ hybridisation analysis. In 9 of the remaining 11 TRCC-like cases (7 male, 4 female, aged 22-84 years), material was available for further study. The morphological spectrum was diverse. Six tumours showed a mixture of cells with eosinophilic or clear cytoplasm in tubular, acinar and papillary architecture. One case was high grade with epithelioid, spindle cell and sarcomatoid areas. Another showed tubular, solid, and papillary areas and foci containing spindle cells reminiscent of mucinous tubular and spindle cell carcinoma. The third showed dyscohesive nests of large epithelioid and histiocytoid cells in a background of dense lymphoplasmacytic infiltrate. By immunohistochemistry, keratin AE1/AE3 was diffusely positive in three tumours, while CK7 strongly stained one tumour and another focally and weakly. CD10 and Pax8 were expressed by eight, AMACR and vimentin by seven, CA-IX by four and TFE3 and cathepsin K by two tumours. Of the two TFE3-positive tumours, one showed polysomy of chromosome 7 and the other of 17; they were VHL normal and diagnosed as unclassifiable RCC. Of the seven TFE3-negative tumours, three showed polysomy of 7/17 and VHL abnormality and were diagnosed as combined clear cell RCC/papillary RCC. One TFE3-negative tumour with normal 7/17 but LOH 3p (VHL abnormality) was diagnosed as clear cell RCC. One TFE3-negative tumour with polysomy 7/17 but normal VHL was diagnosed as papillary RCC, and two with normal chromosomes 7/17 and VHL gene were considered unclassifiable. As morphological features and IHC are heterogeneous, TRCC-like renal tumours can only be sub-classified accurately by multi-parameter molecular-genetic analysis.

OBJECTIVE

To analyze the clinicopathological features of renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusions (Xp11.2 RCC) in our institution.

METHODS

We screened 983 RCC specimens. TFE3 immunohistochemical staining and FISH assay confirmed 22 Xp11.2 RCCs out of 65 suspicious cases. Clinicopathological and treatment outcomes of 22 patients were retrospectively analyzed.

RESULTS

In total, 22 patients included 13 females and nine males with a mean age of 27 years. Ten patients showed gross hematuria. Treatments included surgeries, immunotherapy and molecular-targeted therapy. Seven cases were at stage III/IV and four cases had tumor thrombosis or distant metastasis. During a median follow-up of 34 months, 19 patients were alive while three died of distant metastasis.

CONCLUSIONS

Xp11.2 RCC is rare and FISH proved a useful diagnostic tool. Surgical resection achieved favorable outcome for early disease. Adult patients at advanced stage had poorer outcomes even with postoperative adjuvant therapy.

OBJECTIVE

Xp11.2 translocation renal cell carcinoma (RCC) is characterized by various translocations of the TFE3 transcription factor gene. These rare cancers occur predominantly in children and young adults. Here, we review the clinicopathological features of Xp11.2 translocation RCC.

METHODS

We identified 21 patients with Xp11.2 translocation RCC. We retrospectively analyzed patient characteristics, clinical manifestations, and specific pathological features to assess definitive diagnosis, surgical and systemic treatments, and clinical outcomes.

RESULTS

The mean age at diagnosis was 43.4±20.0 years (range, 8-80 years; 8 males and 13 females). Eleven patients were incidentally diagnosed, nine patients presented with local symptoms, and one patient presented with systemic symptoms. The mean tumor size was 6.2±3.8 cm (range, 1.9-14 cm). At the time of diagnosis, 11, 1, and 5 patients showed stage I, II, and III, respectively. Four patients showed distant metastasis. At analysis, 15 patients were disease-free after a median follow-up period of 30.0 months. Four patients received target therapy but not effectively.

CONCLUSIONS

Xp11 translocation RCC tends to develop in young patients with lymph node metastasis. Targeted therapy did not effectively treat our patients. Surgery is the only effective therapy for Xp11 translocation RCC, and further studies are needed to assess systemic therapy and long-term prognosis.

Xp11 translocation renal cell carcinomas (RCC) are characterized by several different translocations involving the TFE3 gene. Tumors with different specific gene fusions may have different clinicopathologic manifestations. Only 3 RBM10-TFE3 RCCs have been reported to date. Here, we added 4 cases of this rare type of tumors with clinicopathologic, immunohistochemical, molecular, and ultrastructural analyses. Most tumors had similar patterns with mixed architectures as follows: acinar, tubular and papillary patterns of epithelioid cells combined with sheets of small cells with "pseudorosette-like" architectures, mimicking the typical morphology of t(6;11) RCC. Cytoplasmic vacuolization, nuclear groove, and psammoma bodies were observed in most cases. Immunohistochemically, all 4 cases demonstrated moderate to strong immunoreactivity for TFE3, Cathepsin K, CD10, Ksp-cadherin, E-cadherin, P504S, RCC marker, PAX8 and vimentin, whereas negativity for TFEB, HMB45, and CK7. CKpan and Melan-A were at least focally expressed. The antibody to Ki-67 showed labeling of 3% to 8% (mean, 5%) of tumor cell nuclei. ;Of interest, several immunostainings demonstrated expression discrepancy in different histology patterns. RBM10-TFE3 fusion transcripts were identified in all cases by reverse transcription-polymerase chain reaction. By fluorescence in situ hybridization, all 4 cases showed unusual split signals with a distance <1 signal diameter (co-localized or subtle split signals) and usually had false-negative results. We also observed ultrastructures, including melanin pigment, nuclear groove, numerous glycogens, mitochondrion with areas of high electron density material, basement membrane material, and cell junctions with poor development. All 4 patients were alive with no evidence of recurrent disease. Our report adds to the known data regarding RBM10-TFE3 RCC.

Sarcoma metastatic to the brain is uncommon and rarely occurs as the initial manifestation of tumor. Alveolar soft part sarcoma (ASPS) is a rare but well-studied subtype of sarcoma. A 39-year-old man presented with seizures due to a left temporal meningeal-enhancing lesion with striking brain edema on MRI. The patient underwent neurosurgical resection for suspected meningioma. Histology showed large tumor cells clustering and forming small nests, in places with pseudoalveolar pattern. Diastase-resistant periodic acid-Schiff revealed very rare granular and rod-like cytoplasmic inclusions. Immunohistochemistry showed convincing positivity only with vimentin and smooth muscle actin. The histological features were strongly suggestive of ASPS. At the molecular level RT-PCR and sequencing analysis demonstrated ASPCR1-TFE3 fusion confirming the histological diagnosis of ASPS. There was no evidence of primary extracranial tumor by physical examination and on chest and abdominal CT scan 11 months after presentation. ASPS typically arise from the soft tissues of the extremities and develop multiple metastatic deposits usually with a long clinical course. This case may represent primary meningeal ASPS although metastatic deposit from an undiscovered primary site cannot be entirely excluded.

BACKGROUND

Alveolar Soft Part Sarcoma (ASPS) is a rare malignant tumor arising from skeletal muscles and occurring usually in young adults. It is a solid chemo resistant tumor. At time of diagnosis the disease is usually advanced and lung metastasis are present in 65% of the cases. The translocation (X; 17), producing an ASPL-TFE3 transcript fusion which is detected on tumoral cells wall, is specific of ASPS. The curative treatment is surgical.

METHODS

We report the case of a child with an ASPS of the tongue and lung metastasis.

CONCLUSIONS

This report presents two particularities. Firstly this type of sarcoma is very exceptional in a 2-year-old child. Secondly ASPS is not usually susceptible to chemotherapy.

Most of the yeast artificial chromosomes (YACs) isolated from the Xp11.23-22 region have shown instability and chimerism and are not a reliable resource for determining physical distances. We therefore constructed a long-range pulsed-field gel electrophoresis map that encompasses approximately 3.5 Mb of genomic DNA between the loci TIMP and DXS146 including a CpG-rich region around the WASP and TFE-3 gene loci. A combined YAC-cosmid contig was constructed along the genomic map and was used for fine-mapping of 15 polymorphic microsatellites and 30 expressed sequence tags (ESTs) or sequence transcribed sites (STSs), revealing the following order: tel-(SYN-TIMP)-(DXS426-ELK1)-ZNF(CA) n-L1-DXS1367-ZNF81-ZNF21-DXS6616- (HB3-OATL1pseudogenes-DXS6950)-DXS6949-DXS694 1-DXS7464E(MG61)-GW1E(EBP)- DXS7927E(MG81)-RBM- DXS722-DXS7467E(MG21)-DXS1011E-WASP-DXS6940++ +-DXS7466E(MG44)-GF1- DXS226-DXS1126-DXS1240-HB1- DXS7469E-(DXS6665-DXS1470)-TFE3-DXS7468E-+ ++SYP-DXS1208-HB2E-DXS573-DXS1331- DXS6666-DXS1039-DXS 1426-DXS1416-DXS7647-DXS8222-DXS6850-DXS255++ +-CIC-5-DXS146-cen. A sequence-ready map was constructed for an 1100-kb gene-rich interval flanked by the markers HB3 and DXS1039, from which six novel ESTs/STSs were isolated, thus increasing the number of markers used in this interval to thirty. This precise ordering is a prerequisite for the construction of a transcription map of this region that contains numerous disease loci, including those for several forms of retinal degeneration and mental retardation. In addition, the map provides the base to delineate the corresponding syntenic region in the mouse, where the mutants scurfy and tattered are localized.

Targeting mTORC1 is a highly promising strategy in cancer therapy. Suppression of mTORC1 activity leads to rapid dephosphorylation of eIF4E-binding proteins (4E-BP1-3) and subsequent inhibition of mRNA translation. However, how the different 4E-BPs affect translation during prolonged use of mTOR inhibitors is not known. Here we show that the expression of 4E-BP3, but not that of 4E-BP1 or 4E-BP2, is transcriptionally induced during prolonged mTORC1 inhibition in vitro and in vivo. Mechanistically, our data reveal that 4E-BP3 expression is controlled by the transcription factor TFE3 through a cis-regulatory element in the EIF4EBP3 gene promoter. CRISPR/Cas9-mediated EIF4EBP3 gene disruption in human cancer cells mitigated the inhibition of translation and proliferation caused by prolonged treatment with mTOR inhibitors. Our findings show that 4E-BP3 is an important effector of mTORC1 and a robust predictive biomarker of therapeutic response to prolonged treatment with mTOR-targeting drugs in cancer.

Forty percent of renal cell carcinomas (RCCs) in childhood are characterized by translocation involving transcription factor E3 (TFE3) family members. Here, we describe a case of TFE3-positive RCC in which metastatic relapse to the mediastinal lymph nodes and pulmonary nodules was treated with single-agent sunitinib, a multitargeted tyrosine inhibitor. Complete radiologic remission was achieved after only 3 courses of treatment, and surgical exploration of metastases failed to identify any residual viable disease. The published experience of sunitinib in TFE-RCC is limited, and prospective evaluation of its activity in a larger number of patients is warranted.

Transcription of the human nonmuscle myosin II heavy chain-A (NMHC-A) gene is regulated via multiple elements located in intron 1, including element F which contains an E-box. In this study we have identified and characterized the factors that are capable of binding to element F. Yeast one-hybrid screening using element F allowed isolation of cDNAs encoding transcriptional factors TFEC, TFE3, and USF2, each of which contains basic helix-loop-helix and leucine zipper motifs. Furthermore, cDNA cloning by polymerase chain reaction yielded cDNAs for two TFEC isoforms, designated TFEC-l and TFEC-s, which are generated by alternative pre-mRNA splicing. In addition to these four factors, USF1, which is known to share the same DNA binding elements with USF2, was isolated for comparison. Electrophoretic mobility shift assays and cotransfection studies of the expression constructs with reporter gene constructs revealed that the above five factors have different binding activities for element F with different transactivation potencies. USF1 and USF2 demonstrate the highest binding activity to element F, yet show the lowest element F-dependent transactivation. TFE3 has a high transactivation potency but the lowest binding activity. TFEC-l demonstrates a high binding activity with the highest transactivation potency, whereas TFEC-s has the same binding activity as TFEC-l with intermediate transactivation. We also demonstrate that an N-terminal activation domain exists only in TFEC-l, whereas a C-terminal activation domain is common to both the l and s isoforms. This study provides the first evidence of TFEC being an activator of transcription, with two separate activation domains.

Dietary phosphate (Pi) is an important regulator for renal Pi reabsorption. The type II sodium-dependent phosphate (Na/Pi) cotransporters (NPT2) are located at the apical membranes of renal proximal tubular cells and major functional transporters associated with renal Pi reabsorption. The yeast one-hybrid system was used to clone a transcription factor that binds to a specific sequence (Pi response element) in the promoter of the NPT2 gene. Two cDNA clones that encoded protein of the mouse transcription factor mu E3 (TFE3) were isolated. TFE3 may participate in the transcriptional regulation of the NPT2 gene by dietary Pi.

Clear cell renal cell carcinoma (CCRCC) is the most common malignant tumor of renal epithelial origin and, with the exception of some rare tumors, the most deadly. The exception is represented by the multilocular cystic CCRCC, whose prognosis is excellent with survival rates of 100% when diagnosis is made according to the WHO definition. For this reason a proposal has been made to rename this tumor as multilocular cystic renal cell neoplasms of low malignant potential. Another exemption could be the clear cell (tubulo) papillary renal cell carcinoma/clear cell papillary renal cell carcinoma (CCPRCC), a tumor with tubulopapillary architecture and clear cytoplasm. Published data indicates that these are neoplasms with indolent clinical behavior. No cases with metastasis have been reported. Neoplasms meeting criteria for CCPRCC will subsequently be reclassified as of "low malignant potential" rather than carcinoma. The stroma of CCPRCC not infrequently demonstrates smooth muscle metaplasia. It should be remembered, however, that smooth muscle stromal metaplasia and proliferation are not entirely specific to this entity. Hence, it is suggested that smooth muscle metaplasia in the kidney may be a nonspecific common reaction to a variety of stimuli. Xp11 translocation renal cell carcinomas are a group of neoplasms distinguished by chromosomal translocations with breakpoints involving the TFE3 transcription factor gene, which maps to the Xp11.2 locus. The most distinctive histologic pattern of the Xp11 translocation renal cell carcinoma is that of a neoplasm with both clear cells and papillary architecture, and abundant psammoma bodies. TFE3 immunohistochemical staining is reported to be sensitive and specific for a diagnosis of translocation-associated carcinoma as long as the labeling is strong, diffuse, and nuclear. This immunostaining is particularly useful if the differential diagnosis includes CCRCC and CCPRCC. In conclusion, recognition of CCRCC and differentiation from other renal cell neoplasms with clear cytoplasm is important not only for prognostication but also for treatment-related reasons.

Sporadic cases of a particular group of renal cancers associated with a translocation involving Xp11.2, known as the TFE3 transcription factor gene, have been reported in the last 20 years. The group was also classified in 2004 WHO kidney carcinoma classifications. A 79-year-old male patient was investigated at the outpatient department for gross intermittent hematuria. Sonography showed a spherical left kidney with increased total size, without evidence of the corticomedullary differentiation due to parenchymal dyshomogeneity with a neoplasm aspect. CT confirmed the sonographic left kidney findings and showed gross node involvement. Angiography did not show any pathological arterial circulation, but massive thrombotic involvement of the renal vein was evident. Radical nephrectomy with thrombectomy and staging lymphectomy were performed. At pathological examination the kidney parenchyma was completely substituted by white firm tissue. Microscopically the tumor was composed of papillary structures lined by epithelial cells with a clear cytoplasm. Multiple node metastases were found. Immunohistochemical examination showed negativity for epithelial markers (cytokeratin and epithelial membrane antigen) and reactivity for CD10 and TFE3. The genetic and histological aspects of this rare tumor are reported. In addition, we describe clinical, radiological and surgical findings.

Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion recently has been found. In this article, we demonstrate an unusual features of such a case. A 73-year-old Japanese woman presented with macroscopic hematuria. The imaging examinations disclosed the renal tumor. Histological examination showed the finding of ASPL-TFE3 RCC, which was characterized by papillary, alveolar, or solid growth of voluminous cell with clear and eosinophilic cells, and stromal psammoma body and hyaline nodules. Additionally, shrunken nuclei, thick cell border, and perinuclear clearing characteristic of chromophobe renal cell carcinoma were observed in the alveolar growth area and the transitional zone between stromal hyalinization, and osseous metaplasia was identified. Immunohistochemically, nuclei of tumorous cell were diffusely positive for TFE3. A RT-PCR study revealed the ASPL-TFE3 chimeric transcript. Finally, pathologists should recognize that the histology of RCC associated with Xp11.2 translocation/TFE3 gene fusion may focally resemble that of chromophobe RCC, but TFE3 immunohistochemistry and molecular genetic study may be helpful in the differential diagnosis. Moreover, osseous metaplasia as well as psammoma bodies should be added to the histological spectrum of the stromal change in RCC associated with Xp11.2 translocations/TFE3 gene fusions.

TFEC is a transcriptional repressor originally identified in rat chondrosarcoma and contains a basic helix-loop-helix and leucine zipper (bHLH/LZ) structure. TFEC shares a closely related bHLH/LZ structure with microphthalmia-associated transcription factor (MITF) and TFE3. In the course of cDNA cloning for a factor structurally related to MITF which is also a regulator for cell differentiation, we have isolated cDNA clones from a THP-1 human monocytic leukemia cell line. These cDNAs encode a protein of 347 amino acids, termed TFECL, a human homolog of a putative rat TFEC isoform. TFECL contains an acidic domain that corresponds to a transcriptional activation domain of TFE3 but its equivalent region is deleted in rat TFEC. We explored a function of TFECL using a melanocyte-specific tyrosinase gene and a ubiquitously expressed heme oxygenase-1 gene, each promoter containing the cis-acting CANNTG motifs. By transient coexpression assays, we showed that TFECL is able to activate or inhibit transcription of a reporter gene linked to either the tyrosinase or the heme oxygenase-1 gene promoter, depending on cell types. These results suggest that TFECL may function as a transcriptional activator under certain conditions.

OBJECTIVE

The aim was to report a multicentric study with a longer follow-up to evaluate the laparoscopic radical nephrectomy in children with renal cancer.

METHODS

This was a retrospective multicentric study, from October 2005 to January 2012, of children who underwent a laparoscopic radical nephrectomy for small renal malignant tumors.

RESULTS

Seventeen children were included in this study. Sixteen underwent chemotherapy before surgery according the SIOP (Société Internationale d'Oncologie Pédiatrique) protocol and one was treated by surgery only for a carcinoma. All except one could be treated by laparoscopy; the biggest tumoral size was 8 cm. The median hospital stay was 3 days (2-10). The pathologic examination showed 15 Wilms' tumors, one clear cell sarcoma and one TFE3 renal cell carcinoma. With a median follow-up of 42 months (range 12 and 77 months) after laparoscopic radical nephrectomy, 15 children had no oncological complications (port site or local recurrence, pulmonary metastasis) and one had a local recurrence without intraoperative tumoral rupture. The child with TFE3 renal cell carcinoma died 4 years after surgery from brain and lung metastases without local recurrence. No small bowel obstruction occurred.

CONCLUSIONS

Radical nephrectomy in children for Wilms' tumor or other renal cancer can be safely performed laparoscopically and our indications can be summarized, for trained laparoscopic surgeons, by small tumors under about 8 cm diameter, especially without crossing the lateral edge of the vertebra on the CT scan at the time of surgery.

In the present study, we explored the expression and correlation of survivin with HIF-1α, TGF-β1 and TFE3 in adenoid cystic carcinoma (AdCC). The expression of survivin, HIF-1α, TGF-β1 and TFE3 was assessed by immunohistochemical staining of a tissue microarray containing tissue samples of normal salivary gland (NSG), pleomorphic adenoma (PA) and AdCC. Correlation analysis of these proteins revealed that increased survivin expression was associated with the overexpression of HIF-1α (P<0.001, r = 0.5599), TGF-β1 (P<0.001, r = 0.6616) and TFE3 (P<0.001, r = 0.7747). The expression of survivin, HIF-1α, TGF-β1 and TFE3 was not correlated with the pathological type of human AdCC (P>0.05). Selective inhibition of survivin by YM155 and siRNA significantly reduced human SACC-83 cell proliferation, with the corresponding decrease in expression of HIF-1α, TGF-β1 and TFE3. The data indicate that the overexpression of survivin in AdCC is related to HIF-1α, TGF-β1 and TFE3. We hypothesize from these findings that the inhibition of survivin may be a novel strategy for neoadjuvant chemotherapeutic and radiosensitive treatment of AdCC.

Microphthalmia-associated transcription factor (MiT) family translocation renal cell carcinoma harbors variable gene fusions involving either TFE3 or TFEB genes. Multiple 5' fusion partners for TFE3 have been reported, including ASPSCR1, CLTC, DVL2, LUC7L3, KHSRP, PRCC, PARP14, NONO, SFPQ1, MED15, and RBM10. Each of these fusion genes activates TFE3 transcription which can be detected by immunostaining. Using targeted RNA-sequencing, TFE3 fusion gene partners were identified in 5 cases of TFE3 immunohistochemistry positive translocation renal cell carcinoma. Three cases demonstrated known fusions: ASPSCR1-TFE3, MED15-TFE3 and RBM10-TFE3. However, two cases showed unreported NEAT1-TFE3 and KAT6A-TFE3 fusion transcripts. The NEAT1-TFE3 RCC arose in a 59-year-old male; which demonstrated overlapping morphological features seen in NEAT2(MALAT1)-TFEB t(6;11) renal cell carcinoma, including biphasic alveolar/nested tumor cells with eosinophilic cytoplasm. The KAT6A-TFE3 renal cell carcinoma demonstrated typical morphological features of TFE3/Xp11 renal cell carcinoma including papillae, eosinophilic cytoplasm with focal clearing and abundant psammoma bodies. KAT6A gene fusion was reported in some cases of acute myeloid leukemia, which has not been previously reported in solid tumors. This report highlights the genetic complexity of TFE3 translocation renal cell carcinoma; and RNA-sequencing is a powerful approach for elucidating the underlying genetic alterations.

OBJECTIVE

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.

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.

Pelvicalyceal system (PS) involvement by renal cell carcinoma (RCC) is staged as pT3a disease (American Joint Committee on Cancer, AJCC, 8^th edition). As papillary RCC (PRCC) has been infrequently represented in studies looking at the prognostic impact of PS involvement, we reviewed our institutional cohort of 8,225 cases for PS involvement by PRCC. Nine such cases were subjected to histopathologic review and immunohistochemistry. FISH for TFE3/TFEB alterations was performed if indicated. One case each (1 of 9, 11%) was classified as TFE3-rearranged and FH-deficient RCC. The majority were high grade (WHO/ISUP grade 3: 8 of 9, 89%) or had features of aggressive disease, including hilar fat (6 of 9, 67%) and regional lymph node involvement (5 of 7, 71%). One low grade 3.3 cm tumor with isolated PS involvement with a germline heterozygous FH p.Lys477dup alteration with retained FH, lack of increased 2SC, BRAFV600E IHC positivity and lack of trisomy 7/17 on chromosomal microarray was identified, arguing against an FH-deficient and conventional PRCC. Our study shows that PS involvement by renal neoplasia with papillary architecture is a rare event. Aside from PRCC, it is important to note that these may include other aggressive and non-aggressive subtypes of renal neoplasia with papillary architecture. One case of isolated PS involvement by a low grade, non-invasive tumor that we refer to as nephrogenic papillary neoplasm, was identified. At present, there is insufficient data to stage such tumors as pT3a (AJCC, 8^th edition) and additional studies are needed to address this question.

Keywords: BRAF p.V600E mutated RCC; FH p.Lys477dup; Nephrogenic papillary renal neoplasia; Papillary renal cell carcinoma; Pelvicalyceal System; Staging.