A 4-year-old male castrated pit bull mix was presented to Cornell’s Oncology Service on 12/5/16 for evaluation of a large, left thoracic body wall mass. Computed tomography revealed a well-defined mass centered on the left 3rd-5th ribs. Chest wall resection of the mass and left 3rd-5th ribs was performed and locoregional metastasis was observed intra-operatively. Histopathology confirmed the diagnosis of hemangiosarcoma. Hemangiosarcoma (HSA) is a common, malignant neoplasm of vascular endothelial cells. The cause of HSA in dogs is unknown, but certain breed predilections suggest a genetic component. HSAs arising from bone is rare, but have been described and have a similar biologic behavior to their visceral counterparts, causing severe local destruction of invaded tissue and a high metastatic potential. Adjuvant chemotherapy was started several weeks post-operatively. Ten months later, our patient continues to receive chemotherapy and has exceeded the median survival time for hemangiosarcoma.