Costal bone changes similar to hypertrophic osteopathy associated with pulmonary and abdominal mesothelioma in a dog

An 8-year-old male Irish Setter was admitted because of nonweight bearing lameness of the left forelimb. Radiography failed to reveal any bony lesions of the forelimb; however, extensive periosteal new bone formation over most rib surfaces and an atypical cardiac silhouette suggestive of a mediastinal mass with pleural effusion were observed. New bone formation was seen on the ilium and a filling defect in the urethra, distal to the prostate, was apparent with contrast urethrocystography. Necropsy revealed scirrhous mesothelioma of the thorax and abdomen, multifocal periosteal exostoses, paraprostatic cyst, and benign prostatic cystic hyperplasia. Tumor cells were associated with the periosteal exostotic costal bone. The specific cause of the lameness was not determined.