Background: Small cell osteosarcoma of bone is a rare form of osteosarcoma, with an incidence rate of 1.3%. This tumor must be differentiated from other small cell malignancies because of treatment considerations, particularly patient response to chemotherapy.
Methods: Clinicopathologic findings in 72 cases (22 from Mayo Clinic files and 50 from consultation files) of small cell osteosarcoma of bone were studied.
Results: The femur was the most common bone involved, although the tumor was found in all portions of the skeleton. Radiographic features (available in 35 cases) suggested a diagnosis of osteosarcoma in 20 cases, Ewing's sarcoma or lymphoma in 14 cases, and giant cell tumor in 1 case. Histologically, there were four types according to the predominant cell size and cytologic features. Osteoid production was identified in all tumors. Complete treatment and follow-up data were available for 45 cases. Generally, in those cases without surgical treatment, greater than 60% of patients died of disease within 2 years. If the surgical procedure was associated with a marginal tumor margin, the prognosis was poor. In the 30 patients with wide or radical surgical margins, at last follow-up 13 were alive with no evidence of disease, 2 were alive with disease, and 15 died of disease at 5 months to 13.1 years after diagnosis. In 16 of 22 Mayo Clinic patients, excluding those who presented with metastasis, the cumulative 5-year survival rate was 28.9%. Median survival time in patients who had surgery with additional chemotherapy was 13.4 years, compared with 1.4 years in patients who underwent surgery alone (P = 0.17).
Conclusions: Small cell osteosarcoma is a definite reproducible histologic entity. Treatment should be based on a protocol for osteosarcoma.