The osteosarcoma is the more common of the bone tumors in dogs, it is characterized by a highly invasive and metastatic behavior. The incidence of presentation in column is low compared to other bony structures, being hindered the diagnosis and treatment.

Female Rottweiler 8 years old and 31 kg of weight was presented to the Veterinary Hospital of Small Species, Autonomous University of the State of Mexico, showing limping in the right member pelvic for 3 months, and the recently development of a nodule in the right iliac cranial crest of size of 11x12.5cm, showing firm consistency, not movable and painful to the manipulation, without antecedents of traumatism.

Radiographic study of abdomen in the projection ventral-dorsal, in the lateral right aspect revealed a 13x7cm oval structure, with density of soft tissue. In this structure, areas with increment of bony density were observed in an irregular way. The fine needle aspiration cytology reported a lipoma. Hemogram and sanguine chemistry didn't have representative changes. The patient was euthanized by owner request.

At necropsy an amorphous and hemorrhagic mass was found, its consistency varied between friable to solid, such mass were covered with a fatty layer of 5 cm of thickness. The tumor invaded muscles and lumbar vertebras without involving the abdominal cavity. Metastasis in kidneys, lungs, mediastinum and popliteal lymph nodes were found. An imprint of tumor revealed an undifferentiated sarcoma.

Histopathologically an osteoblastic productive osteosarcoma was diagnosed, it was characterized by non cohesive osteoblastic cells close to bone spicules and by the presence of myxoid or osteoid intercellular substance. Areas with plump and spindle cells and large foci of calcification and coagulation necrosis were observed. Invasion of cells was detected inside blood and lymphatic vessels besides metastasis to kidney and lung.

The vertebral osteosarcoma is not a very common tumor, diagnose is unfavorable for its localization, is able to destroy the surrounding tissues and to generate metastasis in several organs. The localization, size and behavior of tumor could make difficult the diagnostic with less invasive methods usually used in the veterinary clinic like in this case. Being the histopathologic study the most reliable diagnostic method.