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

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

Multi-institutional Analysis of Immune-Oncology Combination Therapy for Metastatic MiT Family Translocation Renal Cell Carcinoma

SUMMARY

Metastatic translocation renal cell carcinomas (mtRCCs) are rare and aggressive tumors with limited treatment options. Recent studies demonstrated promising activity of immune-oncology (IO) combinations in mtRCC. However, the effectiveness of dual IO combinations versus IO plus VEGF-TKI combinations remains unclear. We conducted a retrospective analysis of IO combinations in mtRCC patients at 4 institutions. Eligible patients had confirmed mtRCC by genitourinary pathologist and received IO combination therapy (IO+IO or IO+VEGF-TKI). Clinical data and treatment outcomes were recorded from the start of systemic therapy. Objective response rate (ORR) was retrospectively evaluated, and time to treatment failure (TTF), and overall survival (OS) were compared for IO+IO and IO+VEGF-TKI groups. We identified 22 mtRCC patients who received IO combinations, all confirmed to have TFE3 rearrangement by FISH. Most patients were female (68%) with a median age of 41 years (16-79). Treatment breakdown included: IO+IO (n=8, 36%) and IO+VEGF-TKI (n=14, 64%). In the evaluable patients for the efficacy analysis, ORR was 14% (1/7) for the IO+IO group and 54% (6/11) for the IO+VEGF-TKI group. With a median follow-up of 32.4 months, the median TTF was 1.2 months and 6.2 months in the IO+IO and IO+VEGF-TKI groups, respectively ( P =0.12). There was no statistically significant difference in median OS between both groups, 36.7 months in the IO+IO group and 15.6 months in IO+VEGF-TKI ( P =0.9). Our findings demonstrate that IO+VEGF-TKI resulted in higher ORR and TTF point estimates without statistically detectable differences, compared with IO+IO therapy. Larger studies are needed to validate these findings and optimize treatment selection.