Case review of perivascular epithelioid cell tumor occurring in patients with Li-Fraumeni syndrome.

Perivascular epithelioid cell tumors (PEComas) belong to a family of rare mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. Li-Fraumeni syndrome (LFS), an autosomal dominant cancer predisposition syndrome, is caused by a germline variant of the tumor suppressor gene TP53. Here, we report the case of a 20-year-old woman with LFS who developed a PEComa of the liver. She was suspected to have LFS because she had developed osteosarcoma (OS) of the femur along with a concurrent transitional liver cell tumor in the right liver lobe at the age of 8 years. She also tested positive for the germline TP53 missense variant c.722 C > T (p.Ser241Phe). She concurrently experienced recurrence of OS and a new-onset liver tumor at the age of 20 years. Thereafter, microwave ablation was performed for the liver tumor because the Magnetic resonance imaging features suggested that the tumor was a hepatocellular carcinoma. Post-ablation biopsy showed that the tumor cells were spindle-shaped and possessed eosinophilic cytoplasm. Immunohistochemistry revealed that the tumor cells expressed HMB45 and focal alpha-smooth muscle actin. Labeling for S100 protein and cytokeratin-AE1/AE3 yielded negative results. Therefore, a diagnosis of PEComa of the liver was made. Among the ten PEComas reported in patients with Li-Fraumeni syndrome so far, all PEComas except the current case were surgically resected, and no cases of recurrence were documented in the follow-up period. Six of the ten PEComas were located in the liver. We think that the possibility of PEComa should be considered when a liver tumor develops in patients with LFS.