Embryonal rhabdomyosarcoma in a Maine Coon cat

Abstract

Junior Mint, a 14 month old castrated male Maine Coon cat, presented to the Cornell University Soft Tissue Surgery Service on August 24, 2004 for evaluation of a caudal abdominal mass. The mass was first noticed at 4 months of age, and had been growing since then. No other complaints were noted by the owner. Upon physical exam, Junior Mint was found to be normal, except for a large non-painful solid mass in his caudal abdomen. Evaluation by ultrasound and CT scan showed the mass to arise from the abdominal body wall. Incisional biopsy of the mass was performed and histopathology revealed the tumor to be an embryonal rhabdomyosarcoma of the abdominal rectus muscle. The definitive treatment was surgical excision of the mass. Rhabdomyosarcomas are rare in domestic species, and the subtype embryonal rhabdomyosarcomas are exceedingly rare. Rhabdomyosarcomas arise from striated muscle and are most often solid painless masses. These masses are most commonly found in the head and neck region, however, incidence throughout the body has been reported. There are two forms of embryonal rhabdomyosarcomas. In the first large round cells (rhabdomyoblasts) dominate the population, while small primitive myotubule cells dominate in the second form. Rhabdomyosarcomas are often locally invasive and have the potential to metastasize to distant locations including regional lymph nodes and the lungs. Since these tumors are so rare, determining a prognosis for patients with embryonal rhabdomyosarcomas is exceedingly difficult. Although, presently there are no published reports of treatment of embryonal rhabdomyosarcomas in cats conventional treatments in humans consists of surgical excision followed by appropriate radiation and chemotherapy.