Bilateral appendicular bone tumors in four dogs.

Bilateral synchronous appendicular bone tumors, occurring in the same bone and same anatomic site within the bone are very rare. This report describes the clinical presentation and oncologic outcome for four dogs with this rare presentation. All cases presented to the authors following a history of unilateral lameness for several weeks. On presentation, case 1 had pain elicited in the contralateral proximal humerus but all the other cases had no abnormalities detectable on physical examination of the contralateral limb. All dogs had technetium 99m ((99m)Tc) nuclear scintigraphy performed that identified bilateral lesions of the distal radii in two dogs, proximal humeri and distal tibiae in one dog each. Thoracic radiographs performed on all dogs showed no evidence of pulmonary metastases. Three dogs were treated with palliative radiation therapy (two dogs received concurrent bisphosphonates) resulting in survival times from initial presentation of 50 days, 193 days, and 523 days, respectively. One dog had stereotactic radiation therapy (SRT) and a surgical limb-salvage performed followed by carboplatin chemotherapy, resulting in a survival time of 926 days from initial presentation. Palliative and curative-intent treatments for the bilateral synchronous appendicular bone tumors resulted in survival times similar to those reported for treatment of a single primary appendicular bone tumor.