Rhabdomyosarcomatous component in dedifferentiated chondrosarcoma.

The case of a 57-year-old male is described with an extended bone tumor in the proximal left femur. The tumor is histologically classified as dedifferentiated chondrosarcoma. Immunohistologic examination revealed a strong positive reaction for desmin mainly in the tumor giant cells in the dedifferentiated areas, whereas chondroblasts in the low grade chondrosarcoma areas reacted negatively with desmin. In accordance with some cross striation in polymorphic tumor cells this points to a rhabdomyosarcomatous component in the dedifferentiated portions of the tumors. Thus, in addition to fibrosarcomatous, osteosarcomatous and malignant fibrous histiocytoma-like areas, our case presents another sarcomatous constituent in dedifferentiated chondrosarcoma.