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 A recent unpublished study evaluating p53 protein expression demonstrated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?").
Transitional cell carcinoma in people and cats: Is it similar to that in dogs?
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.
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 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.