Transitional Cell Carcinoma in the Distal Urethra of a Female Golden Retriever.

Background: Urinary tract tumours represent only 0.5-1% of neoplasms in dogs, and transitional cell carcinoma (TCC) is the most common. It is most common to find TCCs in the trigone region. Diagnosis can be made with image analysis, cytology or histology. With non-infiltrative lesions in the early stages, it is possible to obtain a biopsy by endoscopy. Surgical resection is the treatment option of choice for this tumour. Dogs with poor response to chemotherapy or at an advanced stage of the disease are candidates for palliative treatment. This paper reports an special case of TCC located in the distal urethra of a female dog, obtaining the diagnosis through endoscopy, cytology and immunohistochemistry. Case: A nine-year old, female, neutered Golden Retriever was referred for examination after suffering vaginal bleeding. Vaginal palpation revealed an apparent mass on the vaginal floor. Cytology by imprinting the mass revealed a carcinoma. A vaginoscopy was performed on the patient. An endoscopic examination showed normal vaginal mucosa, but, through the urethra, a mass was observed in the urethral lumen, with thickening and dilatation of the urinary meatus. A tissue biopsy was obtained. Episiotomy was performed to remove the tumour. Histopathological studies diagnosed the mass as transitional cell carcinoma with incomplete surgical margins. An immunohistochemistry analysis of the tumour was performed. Discussion: The location of the tumour in the distal urethra makes this case unusual, as this rarely occurs. There are few reports of this location in bitch dogs and they are usually diagnosed at necropsy. This shows the great advantages of endoscopy for the diagnosis of tumours in the urinary tract. There are few cases of this type of tumour being described at this site, and they are usually diagnosed at necropsy. This report shows the great advantages of urethroscopy for the diagnosis of neoplasias of the urinary tract. In this report, owing to the location of the tumour, cytologic diagnosis (carcinoma) could be made quickly by an impression smear. However, we were unable to determine the precise tumour type, because there were no cells with vacuolated basophilic cytoplasm or signet-ring-shaped cells. Distinguishing TCC from other malignant tumours by cytology is complicated, as they are caused by immaturity and there is a lack of differentiation; so, biopsy is suggested. Endoscopy is the most effective method to obtain biopsies of TCC in the urinary tract. An endoscopic examination can be performed with a rigid or flexible endoscope. In the present case, a videoendoscope with a diameter of 9.2 mm was used, owing to the large dilatation of the urinary meatus. The majority of vesical tumours are diagnosed by contrast and negative double-contrast cystography; however, in this case, they did not reveal the presence of a tumour in the bladder. Immunohistochemistry was positive for monoclonal antibodies for TAG-72 in the present case; this is a common finding in 53% of reported cases. Conventional surgery was performed to resect the tumour, because electrosurgical transurethral resection of TCCs in females can cause some surgical complications. This animal had a favourable response after administering NSAIDs (piroxicam). Treatment was still challenging, owing to the difficulties in surgical resection and the poor response to conventional chemotherapy. [ABSTRACT FROM AUTHOR]