Synovial sarcoma in a dog.

Summary Synovial sarcoma is an uncommon malignant tumour of mesenchymal origin, occurring mainly in the vicinity of a joint. Subsequent invasion of the joint and adjacent bones may occur. Less frequently the tumour may be localized in soft tissues remote from joints. Synovial sarcoma usually affects male middle-aged dogs of large breeds. The rate of tumour growth can vary from very slow to very rapid. The tumour is usually poorly defined and infiltrates the deeper structures. Metastasis and recurrence are common. Wide-field surgical excision of the tumour or amputation of the affected limb are the most frequently used forms of treatment. In the present case the dog, a 7-year-old male Alsatian, had a slowly growing tumour in the vicinity of the hip joint, bilaterally. There was no involvement of the bones surrounding the tumour. Surgical resection was performed and one year later the dog was reported to be normal.