The transitional cell carcinoma (TCC) is a tumor of the urinary bladder. In dogs, it usually arises in the lower neck of the bladder, where it is virtually impossible to surgically remove, and causes a partial or complete obstruction to urination. The urethra (which carries urine outside the body) is affected in over half the patients diagnosed with transitional cell carcinoma; the prostate gland of male animals may also be involved.

The urinary bladder is lined by transitional cells. They protect the body from the caustic urine inside the bladder and maintain this barrier when the bladder stretches and distends with larger volumes of urine. A transitional cell carcinoma is a tumor of the transitional cell lining of the urinary bladder.
While bladder tumors are somewhat rare as types of cancers in pets, more than half (and possibly up to 70%) of the bladder tumors diagnosed are transitional cell carcinomas.
TCC is more common in females with average age at diagnosis of 11 years of age. Shetland sheepdogs, West Highland White terriers, Beagles, and Scottish terriers seem to be predisposed breeds. Beyond this, specifics remain unknown.
Common clinical signs include bloody urine and straining to urinate.
After other causes of straining to urinate and bloody urine are ruled out. A definitive diagnosis of TCC requires a tissue biopsy. Several other types of growths in the bladder, bladder infection, bladder stones, or bladder inflammation can cause similar symptoms as those in dogs with TCC. Some of these other conditions can also cause "masses" to be seen on radiographs or ultrasound, and these other conditions can cause abnormal cells in the urine, which can be mistaken for TCC. Therefore, the diagnosis of TCC requires a tissue biopsy. This is important because the treatment and prognosis depend entirely on exactly what is wrong with the bladder. A tissue biopsy can be obtained by surgery, cystoscopy (insertion of a fiberoptic scope into the bladder and biopsy through the scope), or in some cases with a urinary catheter.
Transitional cell is aggressively malignant and generally grows in an area not very amenable to surgical removal. For dogs with TCC that has not spread beyond the bladder, surgical excision can be considered depending on location of tumor within the bladder. If surgery is not an option radiation therapy, chemotherapy and oral medications are considered. One of the standard recommendations for dogs with TCC is the use of an oral NSAID, Piroxicam.

Survival is affected by the growth rate of the tumor, the exact location of the tumor within the bladder, and whether the tumor has spread to other organs. The average survival in 55 dogs treated with surgery alone (before drugs that could help were identified) was 3 months days. The median survival in dogs treated with early chemotherapy alone at Purdue University was 4 months. Median survival with Piroxicam treatment in 62 dogs with TCC was 6 months. As mentioned above, approximately 35% of dogs receiving chemotherapy have remission, and the average survival is around 12 months. The survival times in all of these studies, however, varied tremendously from dog to dog.