Osteosarcoma of bone and its important recognizable varieties.

Osteosarcoma of bone is a recognizable entity if the histopathologist designates tumors as such when their malignatn cells produce osteoid substance even if only in small foci. Such definition distinguishes this lesion from other sarcomas that arise in bone, especially chondrosarcoma and fibrosarcoma. There is a general tendency to consider that osteosarcomas represent a stereotyped form of disease for which new modalities of treatment can be applied and assessed. The question of whether a given osseous lesion is actually malignant and not a benign neoplasm or even a reactive non-neoplastic condition simulating a malignant tumor may be difficult for the histopathologist. Pathologists without considerable experience in the diagnosis of bone tumors find this question especially vexing. The establishment of a valid diagnosis of osteosarcoma introduces the additional problem that the 11 varieties considered in this paper may pose significant recognizable variations in the clinical capability of the disease. It is apparent that the physician must recognize the known clinicopathologic and prognostic factors of these subtypes in his assessment of the overall problem.