Sclerosing epithelioid fibrosarcoma of the thigh: report of two cases with synchronous bone metastases

We report two cases of sclerosing epithelioid fibrosarcoma occurring in the deep soft tissue of the thigh, confirmed by molecular analysis and associated with bone metastases in the lumbar vertebrae and the iliac wing at the time of diagnosis. Synchronous bone metastases of sclerosing epithelioid fibrosarcoma are extremely difficult to diagnose because clinical and radiological features are not specific. In addition, the range of differential diagnoses is very wide, including metastatic carcinoma and osteosarcoma. At present, all but three published cases of sclerosing epithelioid fibrosarcoma with bone metastases showed bone metastases during follow-up. We confirm in our two cases that the distinct pattern of immunohistochemical staining for MUC4, associated with the absence of staining for both SATB2, a marker of osteoblastic differentiation, and pan-cytokeratin, allows differentiating between sclerosing epithelioid fibrosarcoma and metastatic carcinoma or osteosarcoma.