Osteosarcoma in cats: 22 cases (1974-1984).

Osteosarcoma was diagnosed in 22 cats. Diagnosis was based on results of physical, radiographic, and histologic findings. Fifteen tumors arose from the appendicular skeleton, 4 from the skull, 2 from the pelvis, and 1 from a rib. Radiography revealed that in 14 of 15 cats (93%) with appendicular tumors, the lesion was metaphyseal, primarily lytic, with a "moth-eaten" appearance; absence and presence of periosteal new bone formation were associated with the tumors in 12 and 3 cats, respectively. The remaining 7 cats had axial tumors that were characterized by the presence of periosteal new bone formation in addition to bony lysis. Of the 15 cats with appendicular tumors, 12 were treated by amputation and 3 were euthanatized at the time of diagnosis. Of the cats undergoing amputation for treatment of their appendicular tumors, 6 cats were still alive 64 months after surgery (range, 13 to 64 months); the median survival time of the 5 cats (1 cat was lost to follow-up evaluation) that died was 49.2 months (range, 1 to 122 months). Four of 12 cats (33%) survived greater than or equal to 5 years after diagnosis. Of the cats with axial tumors that were not euthanatized at the time of diagnosis (6 of 7), the median survival time was 5.5 months. Based on these findings, we concluded that cats with appendicular osteosarcoma have a better prognosis than those with axial osteosarcoma, and that amputation is a viable treatment for cats with appendicular osteosarcoma.