Perivascular epithelioid cell tumors (PEComas) of the bone and soft tissue: A Japanese Musculoskeletal Oncology Group (JMOG) multi-institutional study

Abstract

Purpose: Perivascular epithelioid cell tumors (PEComas) of the bone and soft tissues are rare mesenchymal neoplasms, some of which are malignant. However, their clinical and pathological characteristics remain unclear. This study was performed to investigate the clinical and pathological characteristics of PEComas in bone and soft tissues by leveraging information from the Japanese Musculoskeletal Oncology Group. Methods: Ten patients, including four male and six female patients with a median age of 49 years, were retrospectively reviewed. PEComas of the visceral organs, including the uterus and retroperitoneum, were excluded. Results: Nine tumors arose in the soft tissue and one in the bone, with a mean size of 9.3 cm. Four patients showed local recurrence or distant metastasis. The 1-year survival rate was 77%. Pathologically, eight tumors were classified as malignant and two as having uncertain malignancy potential. Half of the tumors showed high MIB-1 index values of >30%. Immunohistochemically, the melanocyte marker HMB45 was expressed in 90% cases, and muscle-specific markers were expressed only in 30–50% cases. Transcription factor binding to IGHM enhancer 3 (TFE3) expression was positive in 89% of the patients. Tumors with high expression of TFE3 were classified as PEComas with malignant potential according to Folpe’s classification. Conclusions: Bone and soft tissue PEComas may have a higher malignancy potential than other visceral PEComas and are more likely to develop as TFE3-rearranged PEComas.