Urothelial cell carcinoma with widespread local and distant metastasis and associated osseous metaplasia in a dog

A 9-year-old female neutered husky-cross dog was referred for investigation of sanguinous vaginal discharge and a painful inguinal mass. On clinical and ultrasound examination, a pedunculated ‘cauliflower-like’ mass was found originating from the vulva with plaque-like masses at the bladder trigone, extending into the bladder neck and the proximal urethra. Bilateral medial iliac lymphadenopathy and a firm, erythematous and painful inguinal dermal thickening measuring 70 mm x 50 mm were also found. During recovery following sedation, the patient developed uncontrollable status epilepticus and was euthanized. Post-mortem examination confirmed the presence of a highly infiltrative urothelial cell carcinoma with widespread local and distant metastases to the medial iliac lymph nodes, lungs, inguinal skin and pelvic musculature. Osseous metaplasia in association with small neoplastic aggregates was noted on histopathology within the pelvic musculature.