An update on diagnosing and treating urinary bladder transitional cell carcinoma in dogs - Veterinary Medicine
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An update on diagnosing and treating urinary bladder transitional cell carcinoma in dogs
These tumors in dogs are difficult to completely resect, so the prognosis for long-term survival is guarded. But new avenues of treatment are being discovered, and treatment protocols already in place can extend and enhance dogs' lives.


VETERINARY MEDICINE



Transitional cell carcinoma in people and cats: Is it similar to that in dogs?
In addition to molecular alterations in canine transitional cell carcinoma, muscle-invasive transitional cell carcinomas in people frequently carry mutations in the p53 and retinoblastoma tumor-suppressor genes.15 This aggressive form of the disease in people closely mimics transitional cell carcinoma in dogs, and these pathways are likely altered in canine transitional cell carcinoma. A recent unpublished study evaluating p53 protein expression demonstrated positive reactivity in four of seven canine transitional cell carcinoma cell lines and no reactivity in normal bladder mucosa.16 These findings are similar to the incidence of mutated p53 genes seen in transitional cell carcinoma in people, further strengthening the apparent similarities between transitional cell carcinomas in people and dogs and supporting canine transitional cell carcinoma as a good comparative model in clinical research (see the boxed text titled "Transitional cell carcinoma in people and cats: Is it similar to that in dogs?").

DIAGNOSIS

When canine bladder transitional cell carcinoma is suspected, an organized diagnostic approach can help to definitively diagnose it and may help to avoid seeding tumor cells to other locations.

Clinical signs

Dogs with bladder transitional cell carcinoma typically present with signs consistent with lower urinary tract disease, including dysuria, hematuria, stranguria, and pollakiuria. The signs have often been present for weeks to months and may appear to wax and wane with temporary clinical response to empirical antibiotic therapy. Occasional presenting complaints may include pain or lameness from bone metastasis or paraneoplastic hypertrophic osteopathy.1

Physical examination

Physical examination may reveal a distended urinary bladder, and rectal examination may reveal thickening of the urethral mucosa and sublumbar or sacral lymphadenopathy. While the bladder mass can often be palpated transabdominally, physical examination may be unremarkable in many dogs with transitional cell carcinoma.

Initial diagnostic tests

In all older dogs with suspected lower urinary tract disease, perform initial diagnostic tests consisting of a complete blood count, a serum chemistry profile, urinalysis, and bacterial urine culture and antimicrobial sensitivity testing. Seeding of the tumor cells along the needle tract while performing cystocentesis has been reported, so, ideally, avoid this procedure if you suspect transitional cell carcinoma.17

Complete blood count and serum chemistry profile results are often normal in dogs with transitional cell carcinoma. Renal or post-renal azotemia may be present if the mass obstructs the ureters or urethra, possibly resulting in hydronephrosis and decreased renal function.

Urinalysis results are often suggestive of cystitis—with red blood cells, white blood cells, and bacteria present. Nonneoplastic, reactive transitional epithelial cells can appear similar to transitional cell carcinoma cells, so use caution when interpreting urine cytology results.

Bladder tumor antigen test

The recently developed bladder tumor antigen test (V-BTA—Polymedco) is a rapid latex agglutination assay used to detect tumor-associated glycoprotein complexes in the urine. Studies show the test to have high sensitivity for detecting transitional cell carcinoma. The specificity, however, is low. False positive results are frequently seen in dogs with nonneoplastic lower urinary tract disease such as infection, proteinuria, and glucosuria.18-20 The test may hold potential as a screening test, and dogs that have positive results should be further evaluated to rule out transitional cell carcinoma and potential nonneoplastic causes.

Histologic examination of biopsy samples

Histologic evaluation of bladder biopsy samples currently remains the only method to definitively diagnose transitional cell carcinoma. Tissue biopsy samples can be obtained by traumatic transurethral catheterization, cystoscopy, or surgical cystotomy. As previously mentioned for fine-needle aspiration of the bladder, avoid ultrasound-guided transabdominal Tru-Cut biopsies because of the risk of needle-tract seeding of tumor cells.


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