Primary sarcoma of the ribs in a large, mixed breed dog

A 9-year-old, 30-kg, neutered male, mixed breed dog was referred for en bloc resection of a tentatively diagnosed costal chondrosarcoma. Light microscopic examination of the excised mass confirmed osteosarcoma. Adjuvant chemotherapy with 4 treatments with carboplatin was initiated. There have been no signs of metastases 5 months postsurgery.