The Istituto Rizzoli experience with small cell osteosarcoma.

Osteosarcoma has been divided into numerous varieties based on clinical, radiographic, and histologic characteristics. Small cell osteosarcoma is a distinct subtype with a histologic appearance in which the bulk of the lesion is composed of round malignant cells with minimal areas of spindle cells. Osteoid production is always present. The lesion may mimic Ewing's tumor and other lesions in which round cells are seen. We report the clinical, radiologic, and pathologic features of this tumor, as well as the clinical outcome and response to therapy.