Tail base tumor diagnosed as chondrosarcoma in Saint Bernard dog

Abstract

A 6‐year‐old male Saint Bernard dog was examined because of a firm nonpainful tail‐base mass. Radiographs revealed an expansile heterogeneous bony mass of the sixth coccygeal vertebra. The tail was amputated. The histologic diagnosis was coccygeal vertebral chondrosarcoma. Chondrosarcomas account for ten to eleven percent of all skeletal tumors and occur commonly in the flat bones in large‐breed dogs. Radiographically chondrosarcomas appear predominantly osteolytic but may contain mottled mineralized densities. In the dog described here the radiographic signs were typical of a malignant cartilaginous tumor: cortical destruction, mottled mineralized densities, ill‐defined margins, and continued but relatively slow growth. However, there was no periosteal reaction and the chondrosarcoma was at an unusual site.