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

Abstract

To describe the spectrum of MRI features, histopathological findings, and clinical outcomes of musculoskeletal PEComas at a single tertiary sarcoma center. 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. 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. 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.