Location: Trunk and craniofacial bones. Rare in the limbs.

Clinical: Pain and swelling.

Imaging: On x-ray – osteolytic lesion with permeative destruction of bone, ill-defined margins, breaking the cortex, with soft tissue mass, and with faded typical calcifications.

Histopathology: Dense round cells proliferation with hemangiopericytoma-like architecture. Within the tissue there are small foci or larger islands of well-differentiated hyaline cartilage.

Course and Staging: Fast growth, high rate of recurrence with inadequate surgery, and frequent metastases. Usually, IIB.

Treatment: Wide or radical resection. Chemotherapy is used but its real effectiveness is not yet known. Prognosis is poor.