Parosteal osteosarcoma: a treatment-oriented study.

Parosteal osteosarcoma carries the best prognosis of all forms of osteogenic sarcoma. In our series of cases, adequate resection of low- and moderate-grade lesions has resulted in long-term survival without any evidence of residual disease. Small lesions of less than 5 cm diameter and low grade cellular atypism are treatable by an en bloc resection with 2.5 cm margins of normal bone. Larger lesions, of Grade I-II malignancy, are more successfully treated by a two-stage resection spaced six months apart. Recurrences of low-grade tumors are also successfully treated by this method. Grade III lesions, and all those with intramedullary involvement, should be treated by measures appropriate for other types of high-grade osteogenic sarcoma. Special problems encountered in resection surgery are managed by prevention of pathologic fracture, bone grafts, avoidance or repair of major neurovascular structures, and preservation of joint function.