Parosteal osteosarcoma. 2-23-year follow-up of 33 patients.

In a study of the working group for bone tumors of the German Orthopedic Society, 33 patients with a histologically confirmed parosteal osteosarcoma at reexamination underwent clinical and radiographic follow-up. Local recurrence occurred in all the cases after intralesional surgery and in 4 of 8 cases after marginal excision. The grade of differentiation was decisive for the prognosis. Despite intralesional surgery, the prognosis for Grade 1 tumors was good. Metastases developed in 1 of 23 patients with a Grade 1 tumor and in 4 of 9 patients with a Grade 2 tumor. The single patient with a Grade 3 tumor was treated with adjuvant chemotherapy and was free of disease after 5 years.