Primary skeletal muscle tumors can be benign (rhabdomyoma) or malignant (rhabdomyosarcoma). Secondary tumors involved with metastatic spread include lymphosarcoma, hemangiosarcoma, and adenocarcinomas. Local tumors (fibrosarcoma, osteosarcoma, mast cell tumors) can invade adjacent muscle. Lipomas can also invade intermuscular tissue spaces.
Clinical signs include localized swelling and lameness. Diagnosis is confirmed by biopsy and histologic evaluation of the samples. Treatment is by surgical excision or limb amputation; chemotherapy and radiation may be used depending on the tumor type.