Mass in bladder seen radiographically in trigone region. Contributor's Diagnosis and Comments. This case is typical of the few reported in the literature, occurring in the trigone region in a young dog. Most of the cells are immature and poorly differentiated. The mass is composed of primitive appearing spindled to stellate cells.
Multinucleate cells are common and occasionally contain a central row of nuclei.
PTAH and Masson's trichrome did not demonstrate cross striations. Cross striations were discernable in sections stained for desmin. Botryoid rhabdomyosarcomas occur most often in large breed dogs under 18 months of age with a high incidence in Saint Bernards. They occur most frequently at or near the neck of the bladder and occasionally in the urethra. Tumors are pale to light tan, variably firm, and the overlaying mucosa is frequently ulcerated, hemorrhagic, and necrotic.