Renal malignant perivascular epithelioid cell tumor: a case report and literature review

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms characterized by melanocytic and smooth muscle differentiation. Although the kidney is a relatively common site, malignant renal PEComa is exceedingly rare, particularly in patients with tuberous sclerosis complex (TSC). Overlapping radiologic features between angiomyolipoma and malignant PEComa often result in diagnostic challenges.

We report an 18-year-old female who presented with right flank pain. Contrast-enhanced CT revealed a large heterogeneous mass in the right kidney (127 × 81 mm) with intratumoral hemorrhage, initially interpreted as angiomyolipoma associated with TSC. Physical examination and family history were suggestive of TSC, and genetic testing confirmed a pathogenic TSC2 frameshift mutation. The patient underwent open right partial nephrectomy. Histopathology demonstrated a malignant PEComa composed of epithelioid cells with focal coagulative necrosis. Immunohistochemistry showed diffuse positivity for Melan-A and smooth muscle actin, focal HMB-45 expression, and a Ki-67 index of approximately 5%. The patient recovered postoperatively; however, CT imaging at one-month follow-up revealed a suspected enhancing mass in the lateral mid-portion of the right kidney, requiring continued close surveillance. Based on the suspected enhancing mass identified at the one-month postoperative CT follow-up and the confirmed malignant potential, the patient has been advised to initiate adjuvant mTOR inhibitor therapy (Everolimus). A rigorous 3-month interval follow-up protocol has been established to evaluate treatment efficacy and prognosis.

This case highlights a rare occurrence of malignant renal PEComa in a young patient with genetically confirmed TSC. Large tumor size, necrosis, and mitotic activity are important indicators of malignant potential. In young patients with TSC and atypical renal masses, malignant PEComa should be considered in the differential diagnosis. Multidisciplinary evaluation, genetic testing, and awareness of emerging mTOR-targeted therapies are essential for optimal management.