Rapidly enlarging malignant abdominal PEComa with hepatic metastasis: a promising initial response to sirolimus following surgical excision of primary tumor.

Intra-abdominal perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors. Although no effective therapies have been agreed upon, mTOR inhibitors are currently being investigated as a potential therapy for this extremely rare tumor. We present a case of a 64-year-old male found to have a large intra-abdominal PEComa with multiple metastatic lesions in the liver. Patient underwent surgical resection of the primary lesion in the abdomen and sigmoid colon followed by adjuvant therapy with the mTOR inhibitor, sirolimus. Initial response was noted with a decrease in size and number of lesions found in the patient's liver. After 8 months of therapy, restaging imaging showed disease progression in the liver lesions. Patient subsequently failed treatments with pazopanib, investigational therapy TAK-228 (Sapanisertib) and nivolumab and ipilimumab. Overall the patient died after 22 months of disease. PEComas generally follow a benign course. This case is a much rarer entity given the malignant features/outcome.