CHONDROMYXOID FIBROMA-LIKE OSTEOSARCOMA - A DISTINCT VARIANT OF LOW-GRADE OSTEOSARCOMA

Chondromyrxoid fibroma-like osteosarcoma is a recently described, extr emely rare subtype of low-grade osteosarcoma. Two such cases were enco untered among 102 cases of osteosarcoma seen in the Prince of Wales Ho spital, Hong Kong, between 1984 and 1994, The first patient, a 39-year -old woman. presented with a mass in her right maxilla which was resec ted and mistaken as a myxoma. The tumour recurred locally four years l ater and she now has extensive local recurrent disease six years after initial presentation and is amenable to support treatment only, The s econd patient, a 28-year-old man, had a pelvic tumour which recurred i n the form of a polypoid left atrial tumour and pulmonary nodules six gears after operation, The left atrial tumour recurred one year after operation. and led to sudden death of the patient seven years after in itial presentation, Radiologically, tile tumours in both cases appeare d as expansile osteolytic lesions with erosion of adjacent bone and in filtration into soft tissue, Histologically, they consisted of lobules of spindle, stellate or polygonal tumour cells showing mitotic activi ty and with moderate nuclear pleomorphism and hyperchromatism, set in a highly myxoid stroma superficially mimicking chondromyxoid fibroma. The histological hallmark was the direct production of osteoid by tumo ur cells. Chondromyxoid fibroma-like osteosarcoma merits recognition a s a distinct variant of low-grade osteosarcoma for which early appropr iate surgery is indicated.