Primary epithelioid leiomyosarcoma of bone. Case report and literature review.

We describe an epithelioid leiomyosarcoma of bone located in the right knee of a 51-year-old woman. Plain radiograph and CT scan revealed a poorly defined lytic and destructive mass in the upper metaepiphyseal right tibia which involved surrounding soft tissues. The lesion was composed of proliferating monotonous round cells with a high mitotic activity with scanty intersecting spindle cell fascicles. Immunohistochemistry of both areas demonstrated a strong positivity for actin (HHF-35 and alpha-SMA) and vimentin, and negative reactions for desmin, keratin (AE1 AE3), epithelial membrane antigen, S-100 protein, factor VIII-related antigen, CD 31 and CD 34. Ultrastructural study confirmed a diagnosis of leiomyosarcoma. This is the first detailed description of the microscopic and radiological features of primary epithelioid leiomyosarcoma of bone.