Extraskeletal osteosarcomas in dogs: a retrospective study of 169 cases (1986-1996).

Extraskeletal osteosarcomas (EOSs) are rare tumors that arise in various soft-tissue sites (e.g., gastrointestinal tract, subcutaneous tissue, spleen, liver, skin, kidney, urinary bladder, muscle, thyroid gland, eye, and mammary glands). Soft-tissue osteosarcomas (STOs) occur in older dogs with no sex predilection; beagles and rottweilers are at higher risk. Mammary gland osteosarcomas (MGOs) occur in older females; mixed-breed dogs, German shepherd dogs, and miniature poodles are at higher risk. The median survival time for cases with STO was 26 days, and the major cause of death was local recurrence (92%). The median survival time for cases with MGO was 90 days, and the major cause of death was pulmonary metastasis (62.5%).