Challenges in Diagnosing Metastatic Uterine PEComa: Insights from Two Case Studies.

BACKGROUND Perivascular epithelioid cell tumor (PEComa) is usually a benign perivascular tumor that expresses both melanocytic and myogenic cell markers. We report 2 cases of advanced malignant uterine perivascular epithelioid cell tumor (PEComa) in a 74-year-old woman and a 50-year-old woman undergoing surgery in our center. CASE REPORT Case 1: A 74-year-old woman presented with a painful and massive abdominal mass. The imaging revealed a 19-cm necrotic mass close to the mesentery, a suspicious lesion in the uterus, and a probable liver metastasis. The pathological diagnosis was quite difficult with mixed features of leiomyosarcoma and PEComa with an uncommon immunohistochemistry staining pattern. Therefore, we gave a diagnosis of sarcoma with PEComa-like features. Case 2: A 50-year-old woman with metrorrhagia and abdominal pain. Imaging revealed a 7-cm mass in the uterus and suspicious metastatic lesions in the lung and the liver. The immunohistochemistry pattern was typical, with a strong positivity of Human Melanoma Black-45 (HMB-45) and focal positivity of H-Caldesmon. The patient benefited from targeted adjuvant therapy (MTOR inhibitor-based), with 8-month a follow-up showing no recurrence for this Grade IV PEComa mutated for TP53, ATRX, and TSC1. CONCLUSIONS We have report 2 cases of metastatic PEComa with different clinicopathological features. An overlap remains between characteristics of PEComas and smooth-muscle tumors. At present, there are no known pathognomonic findings or specific diagnostic markers.