FBJ virus was injected i.p. into 145 neonatal NIH Swiss [N:NIH(s)] mice. Eighty mice developed a total of 110 neoplasms by 5 months of age. The mean latent period of the tumors was 71 days (26 to 145) postinjection. The frequency of occurrence of neoplasms at different sites was: diaphragm, 45%; ribs, 14%; vertebrae, 14%; femora, 9%; pelvic bones, 5%; tibiae, 4%; sternebrae, 3%; and inguinal area, 7%. The neoplasms were characterized histologically by elongated or rounded cells associated with an abundant connective tissue stroma. Occasional areas of bone formation and apparent osteoid metaplasia were seen. Bone tumors appeared to arise from periosteal cells, to grow by expansion, and to invade locally, but they failed to metastasize. Neoplasms of the diaphragm originated in the central aponeurosis and appeared histologically similar to bone neoplasms. Histochemical studies demonstrated abundant alkaline phosphatase in tumor cells, and ultrastructural observations revealed subcellular characteristics of osteoblasts and chondroblasts. Tumors were readily transplantable and had histopathological characteristics similar to those of the primary viral-induced tumors. The results of this study indicate that the FBJ virus induces in NIH Swiss mice a unique type of chondroosseous neoplasm derived from periosteal cells which has a resemblance to human juxtacortical (parosteal) osteosarcoma.
Alkaline Phosphatase Animals