OBJECTIVE

To describe demographic, therapeutic and follow-up data of four cases of renal cell carcinoma with Xp11.2 translocation in adults older than 50 years of age.

METHODS

Between January 2008 and December 2011, 170 patients underwent surgery for renal cell carcinoma in our center. Systematic histopathologic analysis of specimen removed was performed. Complementary immunohistochemical analysis was performed only in cases with uncertain diagnosis or in patients younger than 40 years of age.

RESULTS

Among these 170 patients with a median age of 59years old (21-89), immunohistochemistry helped find a TFE3 translocation in four cases (2.4%). There were three women and one man of 53, 71, 75 and 86years old respectively. One patient was metastatic at diagnosis. Radical nephrectomy was first performed in all cases. TNM staging was T3aN2R0, T3bN0R0, T2N2R0 and T3aN2R2, with a Furhman grade of 4. Two patients progressed with metastasis 5 and 7months after surgery, and two with lymphatic invasion 2 and 9months after nephrectomy. One patient died during follow-up.

CONCLUSIONS

Xp11.2 translocation renal cell carcinoma was uncommon after 50years of age in our series, but probably under estimated. It seemed to be associated with a poor prognosis. Larger studies must be performed to optimize its specific treatment.

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

OBJECTIVE

To investigate the clinical features of pediatric Xp11.2 translocation renal cell carcinoma (RCC).

METHODS

A retrospective review of 22 cases over 35 years.

RESULTS

Xp11.2 translocation RCCs were identified in 13 boys and 9 girls with a median age of 10.5 years (range: 2.5-16 years). RCC presented with hematuria in 17, abdominal mass in 1, abdominal masses with hematuria in 2, abdominal pain with hematuria in 1, and as an incidental finding in 1 patient. Ten patients were classified stage I, 10 were stage III, and two were stage IV. Of the 10 patients with stage I RCCs, 3 patients with tumor measuring less than 7 cm had nephron-sparing surgery (NSS) and 17 patients underwent simple nephrectomy. A 15-cm tumor was incompletely removed in one patient and another patient with a 25-cm × 18-cm × 15-cm tumor had gross residual. Of the 15 patients followed up between 6 months and 35 years, 13 were still living and 2 had died after surgery.

CONCLUSIONS

Xp11.2 translocation RCC is the predominant form of pediatric RCC, associated with advanced stage at presentation. Nephrectomy is the usual treatment for RCC but NSS is an option for patients with tumors measuring<7 cm. Patients with N+M0 maintained a favorable prognosis following surgery alone.

The disease concept of clear cell (tubulo) papillary renal cell carcinoma (CCP-RCC) as a distinct subtype of renal cell carcinoma has been recently established. First described in the setting of end stage renal disease, this tumor type is more frequently recognized and encountered in a sporadic setting. In this article, we provide an overview of the recent understanding of this tumor. Macroscopically, tumors are well circumscribed with well-developed tumor capsule. Histologically, the tumor cells are cuboidal to low columnar cell with clear cytoplasm and papillary and tubulo-papillary configuration. Immunohistochemically, tumor cells generally show diffuse expression for cytokeratin 7, CA9 (cup-shaped pattern), HIF-1, GLUT-1 and high molecular weight cytokeratin, but negative for AMACR, RCC Ma and TFE3. CD10 is negative or focally positive in most tumors. Genetically, this tumor has no characteristics of clear cell RCC or papillary RCC. Prognostically, patients with CCP-RCC behave in an indolent fashion in all previously reported cases. In conclusion, although this tumor has been integrated into recent International Society of Urologic Pathology Classification of renal neoplasia, both aspects of disease concept and clinical behavior are yet to be fully elucidated. Further publications of large cohorts of patients will truly help understand the biologic potential and the molecular underpinnings of this tumor type.

The incidence of kidney cancer is gradually increasing, with a rate of 2-3% per decade. The kidney develops various kinds of neoplasms, some of which are associated with familial cancer syndromes. Such cases have provided clues to identify the cancer-responsible genes. In 2004, the World Health Organization published a new classification system of renal neoplasms, incorporating recent knowledge obtained in the cytogenetic and molecular biological fields, i.e. genes responsible for each histologic subtype (von Hippel-Lindau for clear cell renal cell carcinoma, c-met for papillary renal cell carcinoma type 1, etc.). Subsequently, the Japanese classification system in 'the General Rule for Clinicopathological Study of Renal Cell Carcinoma' has been revised as the 4th edition, according to the World Health Organization system. Several novel subtypes have been introduced, i.e. mucinous tubular and spindle cell carcinoma, and Xp11.2/TFE3 translocation-associated renal cell carcinoma. Even after the publication of the classification, other novel subtypes have emerged, i.e. acquired cystic disease-associated renal cell carcinoma and tubulocystic renal cell carcinoma. Additionally, some of the subtypes seem to form families based on morphological transition, immunohistochemical features and gene expression profile. In future, the classification of renal cell carcinoma should be reorganized on the basis of molecular biological characteristics to establish personalized therapeutic strategies.

We present a case of renal epithelioid angiomyolipoma (eAML)/perivascular epithelioid cell tumor (PEComa) with a TFE3 gene break visible by fluorescence in situ hybridization (FISH). Histologically, the tumor was composed of mainly epithelioid cells forming solid arrangements with small foci of spindle cells. In a small portion of the tumor, neoplastic cells displayed nuclear pleomorphism, such as polygonal and enlarged vesicular nuclei with prominent nucleoli. Marked vascularity was noticeable in the background, and perivascular hyaline sclerosis was also seen. Immunohistochemically, neoplastic cells were diffusely positive for α-smooth muscle actin and melanosome in the cytoplasm. Nuclei of many neoplastic cells were positive for TFE3. FISH analysis of the TFE3 gene break using the Poseidon TFE3 (Xp11) Break probe revealed positive results. Reverse transcriptase-polymerase chain reactions (RT-PCR) for ASPL/TFE3, PRCC/TFE3, CLTC/TFE3, PSF/TFE3, and NonO/TFE3 gene fusions all revealed negative results. This is the first reported case of renal eAML/PEComa with a TFE3 gene break, and it has unique histological findings as compared to previously reported TFE3 gene fusion-positive PEComas. Pathologists should recognize that PEComa with TFE3 gene fusion can arise even in the kidney.

The Hematopoietic- and neurologic-expressed sequence 1 (Hn1) gene encodes a small protein that is highly conserved among species. Hn1 expression is upregulated in regenerating neural tissues, including the axotomized adult rodent facial motor nerve and dedifferentiating retinal pigment epithelial cells of the Japanese newt. It is also expressed in numerous tissues during embryonic development as well as in regions of the adult brain that exhibit high plasticity. Hn1 has also been reported as a marker for human ovarian carcinoma and it is expressed in high-grade human gliomas. This study was directed toward understanding the function of Hn1 in a murine melanoma cell line. Hn1 mRNA and protein were identified in B16.F10 cells and in tumors formed from these cells. Inhibition of Hn1 protein expression with siRNA increased melanogenesis. Hn1-depleted cells expressed higher levels of the melanogenic proteins tyrosinase and Trp2 and an increased interaction between actin and Rab27a. The in vitro cell growth rate of Hn1-depleted cells was significantly reduced due to G1/S cell cycle arrest. This was consistent with a reduction in the phosphorylation of retinoblastoma protein as well as lower levels of p27 and increased expression of p21. Decreased expression of c-Met, the receptor for hepatocyte growth factor, was also detected in the Hn1-depleted cells, however HGF-dependent stimulation of phosphorylated-ERK was unaffected. Hn1 depletion also led to increased basal levels of phosphorylated p38 MAPK, while basal ERK phosphorylation was reduced. Moreover, Hn1-depleted cells had reduced expression of transcription factors MITF and USF-1, and increased expression of TFE3. These data, coupled with reports on Hn1 expression in regeneration and development, suggest that Hn1 functions as a suppressor of differentiation in cells undergoing repair or proliferation.

The authors describe the computed tomography (CT) and magnetic resonance imaging (MRI) findings of an 18-year-old man with renal cell carcinoma (RCC) associated with the Xp11.2 translocation/transcription factor E3 (TFE3) gene fusion (Xp11 translocation carcinoma). The lesion was hyperdense on unenhanced CT, hypovascular on contrast-enhanced studies, hypointense on T2-weighted MR images, and hemosiderin deposition was suspected on phase-shift gradient-echo MR images. Histopathological specimens revealed pathological findings resembling papillary RCC predominantly and exhibited immunoreactivity for TFE3. Because there is often considerable morphological overlap between this carcinoma and papillary RCC, the imaging findings of Xp11 translocation carcinoma may be similar to those of the papillary subtype. Therefore, Xp11 translocation carcinoma should be considered, particularly in young patients when radiologic images demonstrate a renal tumor mimicking the papillary subtype.

Clathrin is a protein expressed ubiquitously that has important functions in membrane trafficking and mitosis. Two different gene fusions involving clathrin heavy chain (CHC) have been described in human cancers. These involve either anaplastic lymphoma kinase (ALK) or transcription factor binding to IGHM enhancer 3 (TFE3) and raise the possibility that altered clathrin function in cells expressing the fusion proteins could contribute to oncogenesis. In the present study, we tested the functions of CHC-ALK and CHC-TFE3 in endocytosis and mitosis. CHC-ALK is comparable to full-length CHC in both functions indicating that malignant transformation in cells expressing CHC-ALK is not because of any change in clathrin function. CHC-TFE3 is not functional in endocytosis, but can substitute for CHC in mitosis. CHC-TFE3 causes prolonged interphase that is attributed to the TFE3 portion of the protein. We also describe how CHC-TFE3 is a dimer. This suggests that clathrin's proposed role in intermicrotubule bridging can be fulfilled not only by trimers but also by dimers. Finally, this study shows that the membrane trafficking and mitotic functions of clathrin are independent and separable.

The molecular networks that control the progression of chronic kidney diseases (CKD) are poorly defined. We have recently shown that the susceptibility to development of renal lesions after nephron reduction is controlled by a locus on mouse chromosome 6 and requires epidermal growth factor receptor (EGFR) activation. Here, we identified microphthalmia-associated transcription factor A (MITF-A), a bHLH-Zip transcription factor, as a modifier of CKD progression. Sequence analysis revealed a strain-specific mutation in the 5' UTR that decreases MITF-A protein synthesis in lesion-prone friend virus B NIH (FVB/N) mice. More importantly, we dissected the molecular pathway by which MITF-A modulates CKD progression. MITF-A interacts with histone deacetylases to repress the transcription of TGF-α, a ligand of EGFR, and antagonizes transactivation by its related partner, transcription factor E3 (TFE3). Consistent with the key role of this network in CKD, Tgfa gene inactivation protected FVB/N mice from renal deterioration after nephron reduction. These data are relevant to human CKD, as we found that the TFE3/MITF-A ratio was increased in patients with damaged kidneys. Our study uncovers a novel transcriptional network and unveils novel potential prognostic and therapeutic targets for preventing human CKD progression.

The molecular pathogenesis of alveolar soft part sarcoma, a rare tumor with uncertain histogenesis, was elucidated recently and was shown to be due to a translocation between chromosome 17q25 and Xp11 resulting in a fusion product between TFE3 (a transcription factor gene) at chromosome Xp11 and a novel gene designated as ASPL at chromosome 17q25. This results in the transcriptional dysregulation in the pathogenesis of this neoplasm. Of the 12 cases reported so far, the translocation was due to non-reciprocal translocation in 11 cases with only one case demonstrating a reciprocal translocation with respective fusion products. We report yet another case with reciprocal translocation between chromosomes 17q25 and Xp11 with TFE3/ASPL fusion product who presented with metastatic disease. A standard cytogenetic analysis of primary tumor cells with G-banding revealed an abnormal karyotype: 46, X, t(X;17)(p11;q25)[15]/46,XX[5]. PCR analysis of the frozen tumor tissue revealed a type 1 fusion product as described in the literature. We demonstrate a rare cytogenetic abnormality in ASPS, namely reciprocal translocation between chromosomes 17q25 and Xp11 with demonstration of molecular fusion product between TFE3 and ASPL in a patient who initially presented with pulmonary metastases.

CONCLUSIONS

: Alveolar soft part sarcoma (ASPS) is an uncommon neoplasm that has only rarely been reported in the female genital tract. We report a case of incidentally discovered ASPS in the uterine cervix of a 39-year-old woman that exhibited immunoreactivity for TFE3, a recently described marker of ASPS. Strong nuclear immunoreactivity for TFE3 in tumors characterized by a chromosomal translocation involving the TFE3 gene has been reported in ASPS and a subset of pediatric renal cell carcinomas. This translocation, t(X;17)(p11;q25), fuses the TFE3 transcription factor gene on Xp11 to a novel gene on 17q25, designated ASPL. In our case, the neoplastic nuclei were strongly positive for TFE3. To the best of our knowledge, this is the first report of ASPS of the female genital tract with immunoreactivity for TFE3. Other interesting findings in our case were the small size of the tumor and the absence of clinical symptoms.

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.

Rare renal epithelial neoplasms have been recognized to have an angioleiomyoma or leiomyoma-like proliferation of stromal smooth muscle; however, the nature of these tumors and their relationships to other renal cell carcinomas are poorly understood. We analyzed 23 such tumors for their clinicopathological, immunohistochemical, and cytogenetic features using fluorescence in situ hybridization. Twelve showed a homogeneous combination of features and were reclassified as renal cell carcinoma with angioleiomyoma-like stroma. These were composed of neoplastic glandular structures lined by cells with mixed clear, pale, and eosinophilic cytoplasm forming occasional papillary tufts. The stroma resembled smooth muscle and often extended away from the epithelial component, entrapping perinephric fat or non-neoplastic renal elements. Immunohistochemistry showed the epithelium to have reactivity for: carbonic anhydrase IX, CD10, vimentin, cytokeratin 7, cytokeratin 34βE12, and PAX8 but not α-methylacyl-coA-racemase. The stroma labeled for smooth muscle (smooth muscle actin 3+, desmin 1+, caldesmon 3+) but not epithelial antigens. Neither component showed substantial reactivity for HMB45, melan-A, cathepsin K, or TFE3 protein. An interrupted, conspicuous layer of CD34-positive endothelial cells rimmed the epithelium, imparting a two-cell layer pattern resembling myoepithelial or basal cells. Chromosome 3p deletion and trisomy 7 and 17 were uniformly absent. Follow-up was available for three patients, none of whom experienced malignant behavior. Eleven tumors were excluded from this category and considered to be clear cell renal cell carcinoma with a reactive proliferation of smooth muscle (n=4) or tangential sectioning of the pseudocapsule (n=2), renal cell carcinoma unclassified (n=4), or clear cell papillary renal cell carcinoma (n=1). In summary, renal cell carcinoma with angioleiomyoma-like stroma is a distinct neoplasm with characteristic morphological, immunohistochemical, and molecular features, unrelated to clear cell renal cell carcinoma. The immunoprofile overlaps partly with that of clear cell papillary renal cell carcinoma, though morphology and reactivity for CD10 are points of contrast.

BACKGROUND

Alveolar soft part sarcoma (ASPS) is a rare mesenchymal tumor characterized by ASPL-TFE3 translocation. Apart from complete surgical resection, there is no standard management strategy.

METHODS

The clinical data of 69 children and young adults less than 30 years old with ASPS diagnosed from 1980-2014 were retrospectively collected from four major institutions.

RESULTS

Median age at diagnosis was 17 years (range: 1.5-30). Forty-four (64%) were female. Median follow-up was 46 months (range: 1-409). Most common primary sites were limbs (58%) and trunk (24%). ASPL-TFE3 translocation was present in all 26 patients tested. IRS postsurgical staging was I in 19 (28%), II in 7 (10%), III in 5 (7%), and IV in 38 (55%) patients. The 5-year event-free survival (EFS) and overall survival (OS) were 38% and 72%, respectively. The 5-year EFS and OS were 80% and 87%, respectively, for the 31 patients with localized tumors (IRS-I-II-III), and 7% and 61%, respectively, for the 38 patients with metastatic tumors (IRS-IV). Of 11 IRS-IV patients who received targeted therapy upfront, two had partial response, six had stable disease, and three had progressive disease. Median time to progression for IRS-IV patients was 12 months for those treated with targeted therapy, 7 months for cytotoxic chemotherapy (N = 15), and 4 months for observation only (N = 6).

CONCLUSIONS

Localized ASPS has a good prognosis after gross total resection. ASPS is resistant to cytotoxic chemotherapy. Although there are no curative therapies for patients with metastatic disease, prolonged disease stabilization may be achieved with targeted therapies.

OBJECTIVE

Some studies have suggested that tubulocystic carcinoma may be related to papillary renal cell carcinoma. We sought to compare and contrast the molecular and immunohistochemical profiles of tubulocystic carcinoma with those of papillary renal cell carcinoma.

RESULTS

Twelve cases of pure tubulocystic renal cell carcinoma were subjected to fluorescence in-situ hybridization assessment of chromosomal number for chromosomes 7 and 17, and for TFE3 translocation. Immunohistochemical labelling for AMACR, p63, cytokeratin 7, PAX8, cytokeratin 20 and carbonic anhydrase IX was assessed in all tumours. No tumour showed gains of chromosomes 7 or 17, or TFE3 translocation by fluorescence in-situ hybridization. Immunohistochemistry revealed all tumours to be non-reactive with antibodies against p63 and cytokeratin 20. Conversely, the antibody against AMACR gave a positive reaction in the neoplastic cells of all tumours. Four tumours showed focal labelling with antibody against carbonic anhydrase IX, and five tumours showed focally positive reactions with antibody against cytokeratin 7. Recurrence and metastatic disease were not found for the patients with available follow-up information.

CONCLUSIONS

Pure tubulocystic renal cell carcinoma is an indolent tumour with a good prognosis. Our data support the distinction of this neoplasm as a separate entity.

Folliculin (FLCN) is an autosomal dominant tumor suppressor gene that modulates diverse signaling pathways required for growth, proliferation, metabolism, survival, motility, and adhesion. FLCN is an essential protein required for murine embryonic development, embryonic stem cell (ESC) commitment, and Drosophila germline stem cell maintenance, suggesting that Flcn may be required for adult stem cell homeostasis. Conditional inactivation of Flcn in adult hematopoietic stem/progenitor cells (HSPCs) drives hematopoietic stem cells (HSC) into proliferative exhaustion resulting in the rapid depletion of HSPC, loss of all hematopoietic cell lineages, acute bone marrow (BM) failure, and mortality after 40 days. HSC that lack Flcn fail to reconstitute the hematopoietic compartment in recipient mice, demonstrating a cell-autonomous requirement for Flcn in HSC maintenance. BM cells showed increased phosphorylation of Akt and mTorc1, and extramedullary hematopoiesis was significantly reduced by treating mice with rapamycin in vivo, suggesting that the mTorc1 pathway was activated by loss of Flcn expression in hematopoietic cells in vivo. Tfe3 was activated and preferentially localized to the nucleus of Flcn knockout (KO) HSPCs. Tfe3 overexpression in HSPCs impaired long-term hematopoietic reconstitution in vivo, recapitulating the Flcn KO phenotype, and supporting the notion that abnormal activation of Tfe3 contributes to the Flcn KO phenotype. Flcn KO mice develop an acute histiocytic hyperplasia in multiple organs, suggesting a novel function for Flcn in macrophage development. Thus, Flcn is intrinsically required to maintain adult HSC quiescence and homeostasis, and Flcn loss leads to BM failure and mortality in mice.

OBJECTIVE

Several entities have been individualized recently within the family of renal neoplasms with papillary features. Clear cell papillary renal cell carcinoma (CCPRCC) was first described in patients with end-stage renal disease, but is also observed in patients with normal renal function. The objective of this study was to document the clinicopathological and immunohistochemical characteristics of CCPRCC, with a special emphasis on cyclin D1 expression.

RESULTS

The patients were 25 men and 17 women, mean age 60.7 years. Seventeen patients had a chronic renal disease. All tumours were stage pT1, with a mean diameter of 2 cm. Six tumours were multifocal. Tumours cells were mainly cuboidal, with clear cytoplasm and low-grade nuclei apically aligned. In all cases, Fuhrman nuclear grade was one or two. No necrosis or vascular invasion was seen. During follow-up (10-72 months), no metastasis or death related to the disease was observed. Immunohistochemistry showed strong and diffuse cytokeratin 7 immunoreactivity in all cases, but no labelling for AMACR or TFE3. There was diffuse nuclear cyclin D1 immunoreactivity in 83% of cases.

CONCLUSIONS

CCPRCC is now a well-characterized entity. This tumour is an indolent and very low-grade neoplasm. Here we report the first study, to our knowledge, demonstrating the overexpression of cyclin D1 immunostaining by this tumour.

Alveolar soft part sarcoma is a rare neoplasm usually arising in the soft tissues of the lower limbs in adults and in the head and neck region in children. It presents primarily as a slowly growing mass or as metastatic disease. It is characterized by a specific chromosomal alteration, der(17)t(X:17)(p11:q25), resulting in fusion of the transcription factor E3 (TFE3) with alveolar soft part sarcoma critical region 1 (ASPSCR1) at 17q25. This translocation is diagnostically useful because the tumor nuclei are positive for TFE3 by immunohistochemistry. Real-time polymerase chain reaction to detect the ASPSCR1-TFE3 fusion transcript on paraffin-embedded tissue blocks has been shown to be more sensitive and specific than detection of TFE3 by immunohistochemical stain. Cathepsin K is a relatively recent immunohistochemical stain that can aid in the diagnosis. The recent discovery of the role of the ASPSCR1-TFE3 fusion protein in the MET proto-oncogene signaling pathway promoting angiogenesis and cell proliferation offers a promising targeted molecular therapy.

It has not been possible to generate naïve human pluripotent stem cells (hPSCs) that substantially contribute to mouse embryos. We found that a brief inhibition of mTOR with Torin1 converted hPSCs from primed to naïve pluripotency. The naïve hPSCs were maintained in the same condition as mouse embryonic stem cells and exhibited high clonogenicity, rapid proliferation, mitochondrial respiration, X chromosome reactivation, DNA hypomethylation, and transcriptomes sharing similarities to those of human blastocysts. When transferred to mouse blastocysts, naïve hPSCs generated 0.1 to 4% human cells, of all three germ layers, including large amounts of enucleated red blood cells, suggesting a marked acceleration of hPSC development in mouse embryos. Torin1 induced nuclear translocation of TFE3; TFE3 with mutated nuclear localization signal blocked the primed-to-naïve conversion. The generation of chimera-competent naïve hPSCs unifies some common features of naïve pluripotency in mammals and may enable applications such as human organ generation in animals.

Cellular adaptation response to a myriad of stressors is key for survival. The lysosomal/autophagy pathway is inextricably connected to the stress response regulation. Two transcription factors, TFEB and TFE3, have recently emerged as master regulators of this degradative pathway. Their function modulating different cellular pathways will be discussed.

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.

Integration of morphological, immunohistochemical, and molecular methods is often necessary for the precise diagnosis and optimal clinical management of sarcomas. We have validated and implemented a clinical molecular diagnostic assay, MSK- Fusion Solid, for detection of gene fusions in solid tumors, including sarcomas. Starting with RNA extracted from formalin-fixed paraffin-embedded tumor material, this targeted RNA sequencing assay utilizes anchored multiplex PCR to detect oncogenic fusion transcripts involving 62 genes known to be recurrently rearranged in solid tumors including sarcomas without prior knowledge of fusion partners. From 1/2016 to 1/2018, 192 bone and soft tissue tumors were submitted for MSK- Fusion Solid analysis and 96% (184/192) successfully passed all the pre-sequencing quality control parameters and sequencing steps. These sarcomas encompass 24 major tumor types, including 175 soft tissue tumors and 9 osteosarcomas. Ewing and Ewing-like sarcomas, rhabdomyosarcoma, and sarcoma-not otherwise specified were the three most common tumor types. Diagnostic in-frame fusion transcripts were detected in 43% of cases, including 3% (6/184) with novel fusion partners, specifically TRPS1-PLAG1, VCP-TFE3, MYLK-BRAF, FUS-TFCP2, and ACTB-FOSB, the latter in two cases of pseudomyogenic hemangioendothelioma, representing a novel observation in this sarcoma. Our experience shows that this targeted RNA sequencing assay performs in a robust and sensitive fashion on RNA extracted from most routine clinical specimens of sarcomas thereby facilitating precise diagnosis and providing opportunities for novel fusion partner discovery.

We explored transcriptional regulation of mouse mast cell protease-9 (mMCP-9), which is implicated in inflammation of the jejunum during helminth infections and tissue remodeling of the uterus during pregnancy. Transcription was positively regulated by microphthalmia-associated transcription factor (MITF), a member of the basic helix-loop-helix-leucine zipper family that binds to the E-box, a CANNTG sequence. The most significant segment for positive regulation by MITF was nt -183 to -177 of the mMCP-9 promoter, CATCATG, which bound MITF-M. In addition, not only other MITF isoforms but also TFE3, another member of the family, activated mMCP-9 transcription through this nucleotide sequence inserted one base within the E-box.