A case series of urinary bladder rhabdomyosarcoma in seven dogs.

Background: Juvenile urinary bladder rhabdomyosarcoma (ubRMS) is a known entity; however, literature regarding its clinical behavior and endoscopic features is scarce. The aim of this study was to describe clinical and endoscopic features, and outcomes of ubRMS in dogs.

Case Description: Dogs undergoing transurethral endoscopy and with a histological diagnosis of ubRMS were retrospectively collected. Seven dogs with a median age of 18 months (range 6-32 months) were included in this retrospective, multicenter, and descriptive study. Median tumor size was 58 mm (range 30-65 mm), and tumor location was bladder neck in three cases, trigone in two cases, and bladder body in two cases. Two dogs had monolateral ureteral obstruction. Two dogs presented with regional lymphadenopathy and one dog had lung lesions suggestive of metastatic disease. A grape-like mass was reported in four cases and solid in two, with variable consistency (two friables, two firms, and two not reported). Tumor treatments included surgery in three cases, surgery, and adjuvant doxorubicin in one case, and palliative therapy in three cases. The overall median survival time (ST) was 45 days. STs were shorter (range 20-45 days) for dogs treated with palliative care than for dogs treated with curative-intent treatment (range 70-120 days).

Conclusion: ubRMS should be considered as a differential diagnosis in young dogs presenting with bladder masses. In this study, ubRMS confirmed its aggressive clinical behavior. Surgery and chemotherapy seem to increase STs but the prognosis remains poor.