TFE3-associated perivascular epithelioid cell tumor with complete response to mTOR inhibitor therapy: report of first case and literature review

BACKGROUND: Perivascular epitheloid cell tumor (PEComas) are characterized by expression of both muscles, most often smooth muscle actin (in ~80% of cases) and melanocytic markers (mainly HMB-45 and Melan A). TFE 3-associated PEComas are new variant which are poorly defined due to their limited reports in literature. These tumors lack response to targeted mTOR inhibitor therapy due to lack of mutation in TSC gene. Hereby, we are reporting a case of TFE3 associated pelvic PEComa showing excellent response to Everolimus. CASE PRESENTATION: A 45-year-old female presented with complaint of abdominal mass and bleeding per vaginum for 4 months. She had a history of total abdominal hysterectomy 3 years back in view of abnormal uterine bleeding and exploratory laprotomy 7 months back to remove some pelvic mass. Imaging suggested of ill-defined heterogenous mass of 9.3 x 9.2 x 16 cm involving the uterus, cervix, and upper 1/3 vagina. Multiple omental and peritoneal deposits were also seen, making probable diagnosis of carcinoma endometrium. USG guided biopsy showed cores of fibrous tissue with the presence of cells in sheets with granular eosinophillic cytoplasm; IHC showed positivity for TFE-3, H Caldesmon, GATA-3, and Melan A- and HMB-45; and Ki 67 index was 35%. The basis of above diagnosis of PEComa was made and she was started on Everolimus; repeat imaging after 3 months of therapy showed complete response. CONCLUSION: We are reporting first case of malignant pelvic TFE 3 PEComa showing response to mTOR therapy. Identification of TFE 3 PEComa is important because they showed different biologic behavior then their conventional PEComa.