Urinary bladder rhabdomyosarcoma (sarcoma botryoides) in a young Newfoundland dog.

A 13-month-old female Newfoundland dog suffered from urinary bladder tumor. Histologically the tumor consisted of round or fusiform cells, occasionally having eosinophilic cytoplasms. Apparent mature rhabdomyoblasts possessing elongated eosinophilic cytoplasm and cross striations were infrequently observed. The tumor cells exhibited immuno-positive for anti-myoglobin, desmin and vimentin antibodies. Ultrastructurally, tumor cells have abundant myofibrils in their cytoplasm and Z bands were also detected. The present tumor was diagnosed as a urinary bladder rhabdomyosarcoma in a Newfoundland dog, which has not been frequently reported in dogs.