Invasive Papillary Urothelial Carcinoma in a Bitch

Abstract

Background: Urothelial carcinoma is a malignant epithelial neoplasm that affects the urinary bladder in domestic animals. Gallbladder neoplasms account for approximately 2% of all malignant neoplasms in dogs. Common clinical signs include hematuria, dysuria, pollakiuria, and cystitis. The disease predominantly affects older dogs, although gender predisposition remains controversial. Urothelial carcinoma typically originates in the bladder trigone and has the potential for metastasis. Predisposing factors include urine retention and prolonged exposure of the urothelium to carcinogens. This study reports a case of invasive papillary urothelial carcinoma in 1 bitch.

Case: A 15-year-old mixed-breed bitch presented with hematuria persisting for 15 days. The owner reported a similar episode one year earlier, which had been managed with antimicrobial and anti-inflammatory drugs. Despite repeating the treatment, the hematuria persisted. Abdominal ultrasonography revealed a hyperechogenic, heterogeneous mass in the urinary bladder, adhered to the bladder wall and exhibiting vascularization, suggestive of neoplasia. Cytological examination indicated transitional cell carcinoma, necessitating histopathological evaluation for definitive diagnosis. Pharmacological treatment was initiated; however, the patient’s condition deteriorated, leading to euthanasia. Necropsy revealed a focally extensive, whitish-to-reddish mass in the urinary bladder with an irregular, soft surface, measuring approximately 5.0 cm at its largest dimension. The bladder wall was markedly thickened, and the mass had a nodular, whitish appearance. The kidneys were asymmetrical with an irregular surface, while the liver exhibited moderate lobular pattern alterations. The heart appeared slightly globular, and the lungs contained multifocal, rounded, exophytic nodules. Microscopically, the urinary bladder showed poorly demarcated neoplastic proliferation of urothelial cells arranged in multilayered papillae, infiltrating the submucosa and musculature. The neoplastic structures were supported by discrete fibrous stroma.

Discussion: The diagnosis of invasive papillary urothelial carcinoma was based on clinical presentation, macroscopic findings, and histological analysis. The bitch with 15-years-old, aligning with literature reports that older animals are more commonly affected. While certain breeds, such as West Highland White Terriers, Shetland Sheepdogs, and Beagles, exhibit increased susceptibility, the patient in this case was of mixed breed. Urothelial carcinoma can develop anywhere within the renal pelvis and urethra, with the urinary bladder being the most common site, particularly the bladder trigone. However, in this case, the neoplasm directly infiltrated the gallbladder wall. Although urothelial carcinoma is not rare in dogs, recurrent lower urinary tract symptoms such as hematuria, dysuria, and cystitis in older animals should raise suspicion for malignancy. Imaging modalities serve as valuable screening tools; however, the definitive diagnosis requires histopathological examination. Most urothelial carcinomas are highly malignant, with limited therapeutic options and poor prognosis. Further research is essential to elucidate the etiology of the disease, enabling the development of preventive strategies and early diagnostic methods to improve clinical outcomes.

Keywords: malignancy, neoplasia, pathology, transitional cells, urinary bladder.

Título: Carcinoma urotelial papilar invasivo em uma cadela

Descritores: células transicionais, malignidade, neoplasia, patologia, vesícula urinária.