Perivascular epithelioid cell (PEComa) tumors of the musculoskeletal system: a case series with MR imaging and histopathologic review.

OBJECTIVE: To describe the spectrum of MRI features, histopathological findings, and clinical outcomes of musculoskeletal PEComas at a single tertiary sarcoma center. MATERIALS AND METHODS: Following institutional ethics approval, orthopedic oncology and pathology databases were searched for histopathologically confirmed musculoskeletal soft tissue PEComas managed between 2000 and 2025. Inclusion required pretreatment MRI. Pulmonary, intra-abdominal/pelvic, and cutaneous lesions were excluded. Demographic and clinical features were reviewed for all cases. MRI examinations were reviewed in consensus by two fellowship-trained musculoskeletal radiologists and archival histopathology by a dedicated musculoskeletal pathologist. RESULTS: Twelve patients met inclusion criteria (7/12 male), mean age 64.3 years (range 16-89 years). One tuberous sclerosis complex (TSC)-associated fibroma-like PEComa appeared as a well-defined periarticular mass with homogeneously low T1 and T2 signal and no significant enhancement. The remaining 11 non-TSC tumors had a mean diameter of 13.0 cm; 10 of 11 were deep to deep fascia, and 6 of 11 showed trans-compartmental extension. Intratumoral nonenhancement consistent with necrosis was present in all 10 contrast-enhanced cases. Neurovascular encasement was identified in 4 of 11 (36%) and osseous invasion in 2 of 11 (18%). All nine histologically evaluable non-TSC cases showed malignant morphology. The overall metastatic rate was 91%, with disease-specific mortality of 64% at a median follow-up of 19 months. CONCLUSION: Musculoskeletal PEComas demonstrate large size, deep location, macroscopic intratumoral necrosis, as well as frequent trans-compartmental extension on MRI. Clinical outcomes reflect aggressive biologic behavior, with high metastatic rates and disease-specific mortality in non-TSC-related PEComas of the musculoskeletal system.