Granular cell tumors overexpress TFE3 without corollary gene rearrangement—Reply

Evaluation of TRIM63 RNA in situ hybridization (RNA-ISH) as a potential biomarker for alveolar soft-part sarcoma (ASPS)

Alveolar soft-part sarcoma (ASPS) is a rare soft tissue tumor with a broad morphologic differential diagnosis. While histology and immunohistochemistry can be suggestive, diagnosis often requires exclusion of other entities followed by confirmatory molecular analysis for its characteristic ASPSCR1-TFE3 fusion. Current stain-based biomarkers (such as immunohistochemistry for cathepsin K and TFE3) show relatively high sensitivity but may lack specificity, often showing staining in multiple other entities under diagnostic consideration. Given the discovery of RNA in situ hybridization (RNA-ISH) for TRIM63 as a sensitive and specific marker of MiTF-family aberration renal cell carcinomas, we sought to evaluate its utility in the workup of ASPS. TRIM63 RNA-ISH demonstrated high levels (H-score greater than 200) of expression in 19/20 (95%) cases of ASPS (average H-score 330) and was weak or negative in cases of paraganglioma, clear cell sarcoma, rhabdomyosarcoma, malignant epithelioid hemangioendothelioma, as well as hepatocellular and adrenal cortical carcinomas. Staining was also identified in tumors with known subsets characterized by TFE3 alterations such as perivascular epithelioid cell neoplasm (PEComa, average H-score 228), while tumors known to exhibit overexpression of TFE3 protein without cytogenetic alterations, such as melanoma and granular cell tumor, generally showed less TRIM63 ISH staining (average H-scores 147 and 96, respectively). Quantitative assessment of TRIM63 staining by RNA-ISH is potentially a helpful biomarker for tumors with molecular TFE3 alterations such as ASPS.

Granular cell tumors overexpress TFE3 without gene rearrangement: Evaluation of immunohistochemistry and break-apart FISH in 45 cases

Transcription factor E3 (TFE3) is a useful marker for tumors with Xp11.2 translocation, including alveolar soft part sarcoma and renal cell carcinoma. Recently, TFE3 overexpression was also found in granular cell tumors (GrCTs). However, the case cohorts of these two studies were limited to only 11 and 6 cases. Whether aberrant TFE3 expression is a common feature of Asian patients with GrCT requires further investigation. In the present study, immunohistochemical staining and TFE3 break-apart fluorescence in situ hybridization (FISH) assay were performed in 45 samples of GrCTs obtained from Chinese patients recruited from three medical centers in northeast China. Diffusive and marked nuclear staining for TFE3 was identified in 11/45 (24%) cases, which was lower than previously reported. Focal or weak TFE3 staining was identified in 13/45 (29%) cases. The remaining 21 cases were negative stained. In addition, GrCTs in subcutaneous tissue exhibited a relatively higher ratio (8/45, 18%) for TFE3 expression, compared with those in other sites. Furthermore, according to FISH data, no rearrangement or amplification of TFE3 was identified in these cases, whether they were positively or negatively stained for TFE3. The results from the present study demonstrated that part of patients GrCTs exhibited TFE3 overexpression, which suggested that this may not be derived from gene rearrangement.

Granular Cell Tumor of the Neurohypophysis With TFE-3 Expression: A Rare Case Report

Granular cell tumor (GCT) rarely involves the central nervous system, and fewer than 100 cases have been reported in English literatures. We herein report a case of a 36-year-old Chinese man with GCT of the neurohypophysis. Magnetic resonance imaging showed one mass located in the hypophysis with heterogeneous contrast enhancement. Pathological examination showed a neoplasm comprising densely packed polygonal cells of ample cytoplasm with abundant eosinophilic granules inside. The nuclei were small with inconspicuous nucleoli and yet without any mitoses. The tumor was positive for S-100, CD68, CD163, lysosome, and vimentin. Translocation factor E-3 (TFE-3) was diffusely nuclear positive although ASPSCR1-TFE-3 fusion was not detected by fluorescence in situ hybridization. GCT of the neurohypophysis is supposed to be considered under differential diagnosis with neoplasms or lesions of histiocytic origin and others such as pituitocytoma and spindle cell oncocytoma. A group of markers such as GFAP, EMA, CD68, S-100, and PAS staining are useful in complementary diagnosis and TFE-3 may be an alternative marker.

Alveolar Soft Part Sarcoma of the Female Genital Tract: A Morphologic, Immunohistochemical, and Molecular Cytogenetic Study of 10 Cases With Emphasis on its Distinction From Morphologic Mimics

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.