A rare case of a malignant hepatic perivascular epithelioid cell tumor (PEComa) with aggressive progression following the relapse of renal pecoma despite everolimus therapy.

A 55-year-old man with tuberous sclerosis complex (TSC) was diagnosed with left renal angiomyolipoma (AML), a group of perivascular epithelioid cell tumors called PEComas. He had received the mTOR inhibitor everolimus, which resulted in a complete response. However, a left renal mass relapsed in two years, followed by the occurrence of a hepatic mass five months later. Renal biopsy yielded no diagnosis because of massive necrosis in the tumor cells of the left kidney; however, pathological evaluation of the hepatic mass revealed a PEComa with pleomorphic cells. Even with continuous everolimus therapy, hepatic PEComa progressed aggressively and occupied the entire liver within a year from the first detection. An autopsy revealed pleomorphic cells with nuclear atypia spreading in the liver, kidney, and lung, which were not present in the renal AML sample prior to the initiation of everolimus therapy. This finding raises the possibility of a malignant transformation of the PEComa under the mTOR inhibitor therapy. While PEComas often present with benign characteristics, there are rare instances where the tumor exhibits malignant behavior. This highlights the importance of careful monitoring and long-term follow-up to ensure early detection and effective management of potential malignancies.