Xp11.2 translocation renal cell carcinoma (Xp11.2 RCC) is a subtype of RCC characterized by translocations involving a breakpoint at the TFE3 gene (Xp11.2). Moderate to strong nuclear TFE3 immunoreactivity has been recognized as a specific diagnostic marker for this type of tumor. However, exclusive cytoplasmic localization of a TFE3 fusion protein was reported in UOK 145 cells, a cell line derived from an Xp11.2 RCC harboring the PSF-TFE3 translocation. If reproducible using immunohistochemistry (IHC), this finding would have important implications for pathologists in the diagnosis of Xp11.2 RCC, calling into question the specificity of nuclear immunoreactivity for TFE3 in these tumors. The purpose of this study was to determine whether the above-noted cytoplasmic localization of the TFE3 fusion protein could be reproduced using IHC. UOK 145 cells and fresh frozen tissue from 2 clinical cases of Xp11.2 RCC found to harbor the PSF-TFE3 gene rearrangement (by cytogenetic testing) were collected. All samples were subjected to histopathologic evaluation by board-certified pathologists, TFE3 IHC, reverse transcription polymerase chain reaction, and Sanger sequencing analysis. A strong nuclear TFE3 immunoreactivity was demonstrated in all samples including the UOK 145 cell line. No cytoplasmic immunoreactivity was seen. Reverse transcription polymerase chain reaction and Sanger sequencing confirmed the previously reported PSF-TFE3 gene fusion between exon 9 of PSF and exon 6 of TFE3 in the UOK 145 cell line and in one of 2 clinical cases of Xp11.2 RCC. A novel PSF-TFE3 gene fusion between exon 9 of PSF and exon 5 of TFE3 was detected in the second clinical case of Xp11.2 RCC.

OBJECTIVE

The family of perivascular epithelioid cell tumours (PEComas) comprises a related group of mesenchymal tumours of uncertain origin that show both smooth muscle and melanocytic differentiation markers. TFE3 nuclear immunoreactivity may be viewed as a supporting marker, as it has been found in a subset of visceral PEComas. We immunohistochemically analysed 17 cases of primary cutaneous PEComas for TFE3, and five of them also for SOX-10, and also analysed them by FISH for TFE3 rearrangement.

RESULTS

PEComas presented as skin-coloured tumours, in 12 women and five men, with a median age of 49.5 years. Tumours showed either a mixed clear cell-epithelioid cell pattern or a monomorphous clear cell pattern. None of the primary cutaneous PEComas showed detectable TFE3 or SOX-10 positivity. FISH assay for TFE3 rearrangement yielded negative results in all of the tested tumours.

CONCLUSIONS

Cutaneous PEComas are mostly composed of clear cells, and, unlike a subset of visceral and deep-seated PEComas, cutaneous PEComas consistently lack TFE3 expression. Owing to the lack of SOX-10 expression, a neural crest origin could not be shown.

Melanotic Xp11 translocation renal cancer is a recently recognized aggressive epithelioid neoplasm with features overlapping between PEComa, carcinoma, and melanoma, in which TFE3 gene fusions coexist with melanin synthesis. These findings support the idea that melanotic Xp11 translocation renal cancer is a distinct variant of the MiT/TFE3 family neoplasms. The authors describe a pigmented renal tumor occurring in a 30-year-old woman with distinct morphology and immunohistochemical characteristics as Xp11 translocation renal cancer.

Xp11.2 translocation renal cell carcinoma (RCC) with transcription factor E3 (TFE3) gene fusion is a rare tumor, and the prognosis of this tumor is poorer compared with that of other subtypes of RCC. The patient presented herein was a 70-year-old man who presented with a solid mass sized ~8.2×6.1 cm in the right kidney and underwent radical right nephrectomy. Following pathological and immunohistochemical (IHC) examination and fluorescent in situ hybridization (FISH), the patient was diagnosed with Xp11.2 translocation RCC with TFE3 gene fusion. These tumors are more commonly encountered in children rather than in adults, and adult Xp11.2 translocation RCC is associated with a poorer prognosis compared with its pediatric counterpart. IHC assay and FISH are important diagnostic methods. However, there is currently no established effective treatment for Xp11.2 RCC.

BACKGROUND

Xp11.2 translocation renal cell carcinoma (RCC) is a rare variety of a kidney neoplasm. We report a case of bilateral Xp11.2 translocation RCC occurring metachronously and discuss this very rare entity with reference to the literature.

METHODS

The patient was a 56-year-old woman who presented with a right renal tumor. The patient had undergone left radical nephrectomy 7 years previously, which resulted in a histopathological diagnosis of clear cell RCC. Open right partial nephrectomy was performed under the presumptive diagnosis of recurrence of clear cell RCC. The present right renal tumor was pathologically diagnosed Xp11.2 translocation RCC. More than 70% of the tumor cells in the present right tumor were strongly positive for transcription factor E3 (TFE3) expression by immunohistochemical analysis with an anti-TFE3 antibody. A break-apart of the TFE3 genes in the bilateral tumors was identified by fluorescence in situ hybridization analysis. Real time-polymerase chain reaction analysis for the alveolar soft part sarcoma locus-TFE3 fusion gene was performed, which gave a positive result in the bilateral tumors. Pathological comparison of each of the tumors might lead to a final diagnosis of Xp11.2 translocation RCC occurring metachronously.

CONCLUSIONS

We present the bilateral Xp11.2 translocation RCC. A combination of immunohistochemical, cytogenetic and molecular biological approaches allowed the final diagnosis of such a rare RCC.

BACKGROUND

Xp11.2 translocation renal cell carcinoma (RCC), a recently recognized distinct subtype of RCC, is characterized by various translocations, all involving the TFE3 transcription factor gene. These rare cancers occur predominantly in children and young adults and comprise about one-third of pediatric RCCs. In the present study, we review the clinical course of Xp11.2 translocation renal cell carcinoma in our institution.

METHODS

We identified eight cases with Xp11.2 translocation RCC between 2007 and 2010 from the pathological archives of the Taipei Veterans General Hospital. We retrospectively analyzed the patients' characteristics, clinical manifestations, and specific pathological features for definitive diagnosis, surgical and systemic treatment and clinical outcome of these rare cancers.

RESULTS

Patients were aged 20 years to 49 years (mean age 28 years) with female predominance (6 females, 2 males). One patient presented with asymptomatic renal mass detected incidentally during abdominal sonography. Four patients complained of flank or abdominal pain, and the other three complained of gross hematuria at initial presentation. The mean tumor size was 9.2 cm (range, 4 cm-17 cm). Seven patients underwent radical nephrectomy for the primary tumor, while one presented with multiple metastases. All cases were confirmed by TFE3 immunohistochemistry, a sensitive and specific marker of tumors with TFE3 gene fusion, which showed positive nuclear staining. Three patients presented initially with metastatic diseases, and another three patients progressed to lung, liver and bone metastases at eight, seven and nine months postoperatively.

CONCLUSIONS

Although RT-PCR and DNA sequencing are the final diagnoses of the molecular identity of Xp11.2 translocation RCC, experienced pathologists could confirm the histologic diagnosis based on the distinctive morphologic features with positive TFE3 immunochemical nuclear stain. Surgical resection is the only treatment. The role of systemic therapy for local recurrence and metastasis remains to be determined.

OBJECTIVE

The purpose of the study was to retrospectively analyze MRI findings of renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2/TFE RCC) in adults.

METHODS

Sixteen patients with Xp11.2/TFE RCC were reviewed retrospectively. The clinical characteristics and imaging features were assessed and then compared between metastatic and non-metastatic subgroups.

RESULTS

The mean age at diagnosis was 47.4 (20-76) years. Seven (44 %) patients were men, and nine (56 %) patients were women. The lesions predominantly exhibited an endophytic distribution (n = 14, 88 %) with a capsule (n = 16, 100 %), accompanied by solid and cystic patterns (n = 12, 75%) and hemorrhage (n = 11, 69 %). The tumors prevalently appeared hyper- to isointense on T1WI (n = 14, 88 %), hypointense on T2WI (n = 13, 81 %), and hyperintense on DWI (n = 16, 100 %) with a lower ADC (P < 0.001) than that of the surrounding tissue. The tumors were less enhanced than the normal renal cortex in all phases with a prolonged enhancement pattern (P ≤ 0.001). In addition, six patients (38 %) developed recurrence or metastases. The RCCs with metastases showed an irregular shape (P = 0.013), an incomplete capsule (P = 0.018), heterogeneous solid-cystic patterns (P = 0.034), and hemorrhage (P = 0.037) than non-metastatic subgroups.

CONCLUSIONS

MRI provides valuable information for the diagnosis of adult Xp11.2/TFE RCCs. Features including irregular shape, incomplete capsule, mixed solid-cystic pattern, and hemorrhage may indicate the occurrence of recurrence or metastases.

The cell-cycle timing of somatic chromosomal translocations in cancer remains poorly understood but may be relevant to their etiology and the mechanism of their formation. Alveolar soft-part sarcoma (ASPS) is a rare malignant soft-tissue tumor of uncertain lineage that provides an opportunity to address this question. The great majority of ASPSs have relatively simple near-diploid karyotypes characterized by an unbalanced der(17)t(X;17)(p11.2;q25), resulting in nonreciprocal fusion of TFE3 with ASPSCR1 (a.k.a. ASPL), with consequent net gain of Xp11.2->>pter and loss of 17q25->>qter. The presence of a normal X along with the der(17)t(X;17) in ASPSs that occur in men has been well described in previous cytogenetic reports and is most readily explained by a translocation in the G2 phase of the cell cycle. To establish whether formation in G2 is a general feature of the t(X;17), we examined polymorphic loci in Xp11.2->>qter in ASPS from 9 women, including 7 with an unbalanced t(X;17). Our analysis showed that all 7 displayed retention of heterozygosity at all informative markers on Xp11.2->>qter, supporting preferential formation of the t(X;17) in the G2 phase of the cell cycle. Given that the two derivative chromosomes of a translocation in G2 would be expected to segregate together half the time, the predominance of an unbalanced der(17)t(X;17) also raises the possibility of a selective advantage in ASPS cells for gain of Xp11.2->>pter or loss of 17q25.3->>qter or retention of an active copy of TFE3.

The renal cell carcinomas associated with Xp11 translocations (Xp11 translocation RCCs) harbor gene fusions involving TFE3, a member of the microphthalmia-associated transcription factor (MiTF) family. In the present study, we identified a novel partner of TFE3, Ewing sarcoma breakpoint region 1 (EWSR1), in an Xp11 translocation RCC. A 57-year-old Japanese woman without special disease history was referred to us for treatment of an RCC. The resected tumor displayed an alveolar growth pattern with high-grade nuclei. The tumor was diffusely positive for TFE3 and cathepsin K. Anchored multiplex PCR revealed a novel fusion, EWSR1-TFE3. Fluorescent in situ hybridization analysis demonstrated the rearrangements of EWSR1 and TFE3. RT-PCR analysis confirmed the chimeric transcript. No neoplasm with EWSR1-TFE3 has been reported so far, in any organ. The results will expand the genomic spectrums of Xp11 translocation RCCs and contribute to better understanding of the roles of the MiTF family in the oncogenic process.

Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant disorder caused by germline loss-of-function mutations in Folliculin gene (FLCN). BHD is characterized by lower lobe-predominant pulmonary cysts with risk of pneumothorax, benign skin tumors (fibrofolliculomas), and renal cell carcinoma, often of an unusual chromophobe/oncocytic hybrid histology. The FLCN protein functions in multiple signaling and metabolic pathways including positive regulation of mechanistic target of rapamycin complex 1 (mTORC1) activity via FLCN's GTPase (GAP) activity for Rag C, positive regulation of Wnt signaling (in mesenchymal cells), and negative regulation of TFE3 nuclear localization. Therefore, FLCN-deficient cells are predicted to have reduced mTORC1 and Wnt activity and enhanced TFE3 activity. Folliculin also has functions in autophagy, mitochondrial biogenesis, cell-cell adhesion, 5' AMP activated protein kinase activity, and other pathways. The specific contributions of these pathways to the lung manifestations of BHD are largely unknown. This review is focused on the pulmonary manifestations of BHD, highlighting selected recent advances in elucidating the cellular functions of FLCN and current hypotheses related to the pathogenesis of cystic lung disease in BHD, including the "stretch hypothesis." We also discuss important knowledge gaps in the field, including the genetic, cellular and physical mechanisms of cyst pathogenesis, and the timing of cyst initiation, which may occur during lung development.

Recently cabozantinib, a tyrosine kinase inhibitor with activity against VEGF, MET, AXL, and downregulating cathepsin K in vitro, has been proposed for the treatment of advanced clear and non-clear renal cell carcinomas. Since it is well known that cathepsin K is expressed in the majority of MiT family translocation renal cell carcinomas, we investigated cathepsin K, MET, AXL, and VEGF in a large series of those tumours, looking for possible predictive markers. We collected the clinicopathological features of 34 genetically confirmed MiT family translocation renal cell carcinomas [26 Xp11 and 8 t(6;11) renal cell carcinomas] and studied them using an immunohistochemical panel including PAX8, cathepsin K, HMB45, Melan-A, CD68 (PG-M1), CK7, CA9, MET, AXL and by FISH for VEGFA and MET. Cathepsin K was expressed in 14 of 26, HMB45 in 8 of 25, and Melan-A in 4 of 23 Xp11 renal cell carcinomas, whereas labelling for CK7 and CA9 was minimal. In t(6;11) renal cell carcinoma, cathepsin K and melanogenesis markers were constantly positive, whereas CK7 and CA9 were negative. None of the 34 carcinomas showed CD68 (PG-M1) and AXL expression. One aggressive Xp11 renal cell carcinoma showed increased VEGFA gene copy number (4-5 copies) with concurrent gains of TFE3 and TFEB. None of the 34 carcinomas showed MET gene amplification, whereas staining for MET was found in 7 of 8 t(6;11) and in 16 of 24 Xp11 renal cell carcinomas, and in the latter cases, when the expression was >50%, correlated with aggressiveness (p=0.0049). In Xp11 renal cell carcinomas, the aggressiveness was also correlated with larger tumour size (p=0.0008) and the presence of necrosis (p=0.027) but not nucleolar grading (p=1). Interestingly, in patients with tumours exhibiting two of three parameters (necrosis, larger tumour size and MET immunolabelling >50%) an aggressive clinical behaviour was observed in 88% of cases. In conclusion, cathepsin K, CD68 (PG-M1), CK7, CA9, and PAX8 is a useful panel for the diagnosis. Larger tumour size, the presence of necrosis and MET immunohistochemical expression correlate with aggressive behaviour in Xp11 renal cell carcinomas, especially in combination. VEGF, MET, cathepsin K but not AXL may be potential predictive markers for targeted therapy in MiT family translocation renal cell carcinomas.

OBJECTIVE

To demonstrate that patients with Xp11.2/TFE3 gene-fusion translocation renal cell carcinoma (RCC), despite having an aggressive course in young adults, could have valid treatment options such as mammalian target of rapamycin (mTOR) inhibitors with good outcomes. Furthermore, to explain possible mechanisms of action of mTOR inhibitors in this type of RCC.

METHODS

We report a case of a 44-year-old man who has been treated with everolimus for a Xp11.2 translocation/TFE3 gene-fusion RCC after 2 previous failed treatments with tyrosine kinase inhibitor. During the follow-up, we evaluated type and duration of response with everolimus.

RESULTS

The patient obtained a long-lasting response of disease of 25 months with everolimus without any symptom.

CONCLUSIONS

We believe that mTOR inhibitors could be a good line option treatment to consider for this type of patients.

A 68-year-old man was followed up with chronic kidney disease. Follow-up CT incidentally detected a tumor at the left kidney and multiple small nodular shadows in the lungs bilaterally. The patient underwent needle biopsy and was diagnosed with Xp11.2 translocation renal cell carcinoma (RCC) pathologically. Hence, laparoscopic nephrectomy was performed. Fluorescence in situ hybridization analysis revealed a break-apart of the transcription factor E3 (TFE3) genes in the left tumor. After 2 months postoperatively, nivolumab and ipilimumab were administered thrice intravenously, considering the intermediate risk by the IMDC risk classification. However, pleural effusion occurred but was removed adequately. Lung metastasis decreased, but new metastasis occurred at the left iliopsoas muscle. Target therapy was performed with axitinib. Unfortunately, he died 6 months later postoperatively. These tumors commonly occur in children than in adults, and very rare in elderly patients. Xp11.2 translocation RCC in the elderly has a poorer prognosis than that in children. To date, no effective treatment for Xp11.2 translocation RCC has been established.

Keywords: Fluorescence in situ hybridization; Xp11.2 translocational renal cell carcinoma.

TFE3-renal carcinoma is rare in adults. Patients with this disease often have a poor prognosis, because it has reached an advanced stage at presentation, and there is lack of an effective therapy. The exact mechanism of its malignant behavior is still unclear. In recent years, a significant relationship between TFE3 fusion protein and hepatocyte growth factor receptor (HGFR)/Met tyrosine kinase activity was reported in several malignancies. We previously reported that phosphorylation of HGFR/Met was associated with malignant aggressiveness and survival in patients with conventional RCC. Here, using immunohistochemical techniques, we examined two types of phosphorylated HGFR/Met (pY1234/1235 and pY1349) in a specimen of a 29-year-old man with TFE3-renal carcinoma. Strong expression of both proteins was detected in carcinoma cells, but not in normal kidney tissues. In addition, they were expressed more strongly in TFE3-renal carcinoma than in conventional RCC. Although tumor was diagnosed at T1N0M0 and the patient received radical nephrectomy, the tumor metastasized to multiple organs, and he died 2 years after surgery. We speculate that upregulated phosphorylation of HGFR/Met could be partly associated with the malignant aggressiveness and poor survival of this patient.

Alveolar soft part sarcoma of the vulvovaginal region is limited to only 8 reported vaginal cases and 1 vulvar case in the English literature. The histogenesis of the tumor remains intriguing with postulates favoring a myogenic versus nonmyogenic origin. A reciprocal translocation for ASPL-TFE3 gene fusion, frequently detected in ~90% of cases, combined with TFE3 protein immunoexpression are highly sensitive and specific methods for diagnostic confirmation. The current report describes a unique case of vulvovaginal alveolar soft part sarcoma showing the classic morphologic features with documentation of TFE3 protein expression and the ASPL-TFE3 gene rearrangement. Furthermore, a brief review of the literature of vulvar and vaginal alveolar soft part sarcoma cases with the various treatment modalities is outlined.

BACKGROUND

Clinical and pathological characteristics of renal cell carcinoma (RCC) of patients younger than 40 years old are not well known. The objective of this study was to analyze these characteristics by comparison to a group of patients aged 58 to 62.

METHODS

Retrospective study of a group of patients aged less than 40 years old (group 1, n=44) and a group of patients aged 58 to 62 years old (group 2; n=106) treated surgically for a renal mass from January 2000 to July 2009. A comparative analysis of clinical, pathological characteristics and of cancer-specific survival was performed. Specific survival was calculated with the Kaplan-Meier method and compared with the Log-Rank test. Univariate and multivariable analysis were performed to assess and quantify the effect of age on cancer-specific survival. Covariates were gender, age group, tumor size, pT stage, histological sub-type and Fuhrman grade.

RESULTS

Clinical and pathological characteristics were similar in both groups (P>0.05) except for histological sub-type (56% of clear cell RCC for group 1 versus 82% for group 2). In the group of patients younger than 40 years, translocation RCC represented 23% of all RCCs. Cancer-specific survival at five years was similar in both groups (80% and 76% for group 1 and 2 respectively, P>0.58). Fuhrman grade was the only independent prognostic factor of cancer-specific survival (P=0.001).

CONCLUSIONS

Patients younger than 40 years were more likely to have a translocation RCC than their older counterparts for who clear cell RCC represented the main histological sub-type. Cancer-specific survival was similar between both groups. Only a systematic specific immunostaining for TFE3 or TFEB will allow to assess the exact incidence and prognosis of this entity.

A cohort of a heretofore not described rare subtype of renal oncocytoma, small cell oncocytoma with pseudorosettes is presented. Patients were 6 women and 4 men with ages ranging from 51 to 76 years. The tumors displayed areas composed of small cells ("oncoblasts") featuring scant cytoplasm and small, round monomorphic nuclei. The small cell areas constituted 15% to 60% of the total tumor volume (mean, 28.5%; median, 22.5%). No necrosis or mitotic activity was discerned. All tumors also contained areas composed of characteristic oncocytes comprising 40% to 85% of the total tumor volume. In all cases, a varying number of pseudorosettes were identified. The pseudorosettes were composed of small globules of (periodic acid-Schiff-positive) hyaline basal membrane-like material surrounded by small "oncoblastic" cells. The immunohistochemical profile was variable, including at least focal positivity for AE1-3 (10/10), cytokeratin 7 (7/10), epithelial membrane antigen (10/10), c-kit (6/10), antimitochondrial antigen (MIA;10/10), PAX-2 (9/10), AMACR (racemase;6/10), CD10 (5/10), parvalbumin (8/10), vimentin (6/10), claudin 7 (10/10), and claudin 8 (3/10). No immunoreactivity for carbonic anhydrase 9, HMB-45, S-100A1, and TFE3 was documented. We found no differences in the immunophenotype in the small cell oncocytes/oncoblasts that formed pseudorosettes and those that did not. However, there were differences in the immunohistochemical profile of classic oncocytes and small cell oncocytes/oncoblasts. Using array comparative genomic hybridization, no chromosomal changes were identified in any of the cases examined (n = 3). No numerical changes of chromosomes 7 and 17 were revealed on fluorescence in situ hybridization analysis (n = 3). In conclusion, we herein present the first study on small cell renal oncocytomas with formation of pseudorosettes. This is a rare subtype of oncocytoma, which may, especially on a core biopsy, present differential diagnostic difficulties. The immunohistochemical profile of these tumors is variable and differs in significant respects from that of conventional renal oncocytoma. Awareness of this entity and its immunohistochemical variability should help in distinguishing this rare tumor from malignant tumors with similar (small cell) histomorphologic features. All tumors behaved in a benign fashion during follow-up (mean, 3.1 years; median, 1 year).

Renal cell carcinoma with TFEB rearrangement (t[6;11][p21;q13]) was initially recognized to be composed of dual populations of large cells with clear cytoplasm and small cells forming rosettes around hyaline material. With increasing awareness, however, the spectrum of described morphology has been found to be more heterogeneous. We report a 54-year-old woman who underwent partial nephrectomy for a 2.4-cm renal mass, composed of fibrosis, hyalinization, calcification, and ossification and a smaller component of epithelioid cells. Immunohistochemical staining revealed diffuse positivity for cytokeratin AE1/AE3 and PAX8, patchy labeling for melan-A, human melanosome, and cathepsin K, and negative caldesmon, smooth muscle actin, TFE3 protein, carbonic anhydrase IX, CD10, cytokeratin 7, epithelial membrane antigen, and inhibin. Fluorescence in situ hybridization confirmed rearrangement of TFEB and not TFE3. Together with one recent case in another report, our findings suggest that extensive sclerosis and ossification may be a less common recurring histology of TFEB-rearrangement renal cell carcinoma.

Renal cell carcinomas (RCCs) with Xp11 translocation (Xp11 RCC) constitute a distinctive molecular subtype characterized by chromosomal translocations involving the Xp11.2 locus, resulting in gene fusions between the TFE3 transcription factor with a second gene (usually ASPSCR1, PRCC, NONO, or SFPQ). RCCs with Xp11 translocations comprise up to 1% to 4% of adult cases, frequently displaying papillary architecture with epithelioid clear cells. To better understand the biology of this molecularly distinct tumor subtype, we analyze the microRNA (miRNA) expression profiles of Xp11 RCC compared with normal renal parenchyma using microarray and quantitative reverse-transcription polymerase chain reaction. We further compare Xp11 RCC with other RCC histologic subtypes using publically available data sets, identifying common and distinctive miRNA signatures along with the associated signaling pathways and biological processes. Overall, Xp11 RCC more closely resembles clear cell rather than papillary RCC. Furthermore, among the most differentially expressed miRNAs specific for Xp11 RCC, we identify miR-148a-3p, miR-221-3p, miR-185-5p, miR-196b-5p, and miR-642a-5p to be up-regulated, whereas miR-133b and miR-658 were down-regulated. Finally, Xp11 RCC is most strongly associated with miRNA expression profiles modulating DNA damage responses, cell cycle progression and apoptosis, and the Hedgehog signaling pathway. In summary, we describe here for the first time the miRNA expression profiles of a molecularly distinct type of renal cancer associated with Xp11.2 translocations involving the TFE3 gene. Our results might help understanding the molecular underpinning of Xp11 RCC, assisting in developing targeted treatments for this disease.

Perivascular epithelioid cell neoplasms (PEComas) are a family of mesenchymal tumors with features of both smooth muscle and melanocytic differentiation, with or without true melanin pigment. The highly variable morphology of PEComas results in a broad differential diagnosis that is also dependent on anatomic site. A subset demonstrates rearrangements involving the TFE3 (Xp11) locus, which can be used in diagnostically difficult cases. Here we describe a case of a melanotic PEComa with NONO-TFE3 fusion occurring in the sinonasal mucosa, as demonstrated by both next-generation sequencing and molecular cytogenetic studies. This case is the first of its kind in the literature and only the second documented PEComa harboring a NONO-TFE3 rearrangement. In light of unequivocal molecular ancillary studies, this case illustrates that PEComa must enter the differential for pigmented lesions of the sinonasal mucosa, where malignant melanoma would be much more likely to occur.

Alveolar soft part sarcoma (ASPS) is a morphologically distinctive neoplasm of unknown differentiation that bears a characteristic gene fusion involving ASPSCR1 and TFE3. ASPS can occur in the female genital tract, but is rare. Eleven cases with an initial diagnosis of ASPS at female genital tract sites were evaluated for their morphologic features and immunoprofile using a panel of antibodies (TFE3, HMB45, melan-A, smooth muscle actin, desmin, and h-Caldesmon). In addition, the presence of TFE3 rearrangement and subsequent ASPSCR1-TFE3 fusion were determined by fluorescence in situ hybridization. Ten tumors retained their classification as ASPS based on their morphologic appearance, immunohistochemical profile, and demonstration of ASPSCR1-TFE3 fusion. The remaining case was reclassified as conventional-type PEComa due to its pattern of HMB45, melan-A, and desmin positivity as well as absence of TFE3 rearrangement. Sites of the 10 ASPS were uterine corpus (3), cervix (2), uterus not further specified (2), vagina (2), and vulva (1). The age of the patients ranged from 15 to 68 years (mean 34 y, median 32 y). The tumors demonstrated a spectrum of morphologic features, but all had a consistent immunophenotype of strong TFE3 nuclear expression and lack of muscle (smooth muscle actin, desmin, h-Caldesmon) and melanocytic (melan-A, HMB45) markers, except focal positivity for HMB45 in 1. Follow-up was available for 4 patients ranging from 1 to 35 months (mean 15 mo, median 25 mo) and they were alive and had no evidence of recurrence or metastasis at last follow-up. Distinguishing ASPS from its morphologic mimics, particularly PEComa, is important due to increasingly efficacious targeted agents such as MET-selective and VEGF signaling inhibitors in the former and mTOR inhibition therapy in the latter.

The diagnosis of solid pseudopapillary neoplasms (SPNs) is challenging because some SPNs share many similar morphological and immunohistochemical features with other pancreatic neoplasms. In this study, we investigated potential diagnostic markers of SPN. Based on the SPN-specific upregulated genes from a previous DNA microarray and proteome study, we selected six immunohistochemical markers [beta-catenin, androgen receptor (AR), lymphoid enhancer-binding factor 1 (LEF1), transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3), fused in sarcoma (FUS), and WNT inhibitory factor 1 (WIF-1)]. We also evaluated the Ki-67 proliferative index to investigate its associations with prognosis. To validate these markers, we studied 91 SPNs as well as 51 pancreatic ductal carcinomas (PDC) and 48 neuroendocrine tumors (NET) as controls. We found frequent and diffuse nuclear expressions of β-catenin (98.9%), AR (81.3%), LEF1 (93.4%), TFE3 (74.7%), FUS (84.6%), and cytoplasmic expression of WIF-1 (96.7%) in SPNs. In contrast, PDCs and NETs showed no expression. (P < 0.001). When beta-catenin, LEF1, and TFE3 staining were combined, the sensitivity and specificity were 100% and 91.9%, respectively. Four (4.4%) SPNs showed distant metastasis and these tumors were associated with a relatively high Ki-67 proliferative index (≥ 5%; P = 0.013). We identified LEF1, TFE3, and AR as putative diagnostic markers of SPN, auxiliary to β-catenin. Incorporated into an immunohistochemical panel, these markers could be beneficial to distinguish SPN from PDC and NET. In addition, we suggest that the Ki-67 proliferative index can be a predictive marker of metastasis in SPNs.