Typical and atypical osteosarcomas: a clinicopathologic study of sixty-two cases.

Of 62 cases of histologically confirmed osteosarcomas, 50 long bone cases aged under 30 years were grouped as "typical" osteosarcoma, and the other 4 long bone cases and 8 short and flat bone cases were grouped as "atypical" osteosarcoma. Gross and microscopic findings of the lesions, postmortem findings, and survival of the patients were compared between the two groups. Small round cell-type tumor cells and relatively well-differentiated foci resembling osteoblastoma were more often found in the atypical than in the typical osteosarcomas. Although patterns of metastasis were not very different between the two groups, 2 of 6 autopsied short and flat bone cases showed no metastasis. Five-year survival rates of both groups were similar, each about 25%. Six patients of the typical and only one of the atypical osteosarcomas are alive without recurrence more than 6 years after amputation.