Cardiac chondrosarcoma producing parathyroid hormone-related protein.

Chondrosarcoma is a malignant tumor characterized by the formation of cartilage. A case of primary cardiac chondrosarcoma of the left atrium developed in a middle-aged male. The preoperative serum concentrations of C-parathyroid hormone-related protein (PTHrP) and calcium were high (413.2 pmol/L and 12.2 mg/dl, respectively), but normalized after resection of the tumor, which measured 7 x 5 x 3.5 cm. The tumor was histopathologically diagnosed as chondrosarcoma, composed of outer atypical chondroid cells and inner pleomorphic and spindle mesenchymal cells mimicking malignant fibrous histiocytoma. Half of the cartilaginous tumor cells and a few pleomorphic cells showed cytoplasmic immunoreactivity for PTHrP. The tumor is a possible example of the functional pleiotropy of chondrosarcoma.