Urinary bladder botryoid rhabdomyosarcoma with widespread metastases in an 8-month-old Labrador cross dog

An 8-month-old crossbred Labrador retriever was presented with a history and clinical signs suggestive of lower urinary tract obstruction. Laboratory results revealed azotaemia and hyperphosphataemia. Ultrasonographic evaluation of the urinary tract showed a mass at the bladder trigone, hydronephrosis, hyrodureter, and suspected metastases to lymph nodes and the liver. Pulmonary metastasis was identified on thoracic radiographs. A post mortem confirmed metastases to the liver, lungs and regional lymph nodes, as well as to the mesenteric lymph nodes, mediastinum, heart, subcutaneous tissue and several muscle groups. A histopathological diagnosis of metastatic botryoid rhabdomyosarcoma (sarcoma botryoides) was made. A review of the literature shows that, although the bladder trigone is a well documented location for this tumour, this case was unique with its widespread metastases to previously undocumented organs. The incidence, embryology, ultrasonographic appearance and treatment of this tumour are discussed.