Bladder cancer Cancers of the bladder and related structures (e.g., the urethra) are relatively uncommon in dogs and very uncommon in cats. The most common type of cancer is known as transitional cell carcinoma, which is a locally invasive tumor usually found at the neck of the bladder where it feeds into the urethra. This cancer typically occurs in older dogs, most often in Beagles, Scotties, Airedales, Shetland Sheepdogs, and Collies. The most common signs of urinary tract cancer are recurrent urinary tract infections, straining to urinate, frequent urination of small amounts, and blood in the urine. In some cases, the cancer can block the outflow of urine, leading to persistent straining but little to no urine flow. Diagnosis begins with a thorough physical examination. It is often difficult to feel these tumors by abdominal palpation, but rectal or vaginal (when applicable) examination may reveal a thickened area at the neck of the bladder. Urinalysis may reveal blood in the absence of infection, or the presence of cancerous cells. Bladder cancer usually does not show up on plain x-rays, so your veterinarian may recommend contrast radiography. In this procedure, dye and/or air are injected into the bladder (through a catheter) to outline the bladder wall. The wall of the bladder can also be visualized using ultrasound. Other tests may include blood work to check overall health, and chest x-rays to look for metastases, which develop in about one-third of affected dogs. Surgical removal of the tumor is the treatment of choice, but this is often difficult without causing damage to the muscles and nerves that control urination, leading to permanent incontinence. In some cases, radiation and/or chemotherapy can be used to control tumor growth and keep your pet comfortable. Unfortunately, the overall prognosis for pets with transitional cell carcinoma is guarded to poor, especially if the cancer has already metastasized to lymph nodes or other organs. The Types of Bladder Cancer Understanding which type of bladder cancer you have is the first step toward getting the right treatment. The bladder is a hollow, sac-like organ in the pelvic area that stores urine before it is excreted. The wall of the bladder has several layers. First, there is a layer of cells lining the inside of the bladder called transitional, or urothelial, cells. Beneath that is a thin layer of connective tissue called the lamina propria. Next is a layer of muscle tissue, and after that is a layer of fatty tissue that separates the bladder from organs next to it. Where the cancer occurs and what type of cells are involved determines the type of bladder cancer you have. Bladder Cancer: Know the Different Types There are four main types of bladder cancer, which are categorized by the way they look under a microscope. Each type of bladder cancer may respond differently to chemotherapy or radiation treatment. 1. Transitional cell carcinoma, also known as urothelial carcinoma: More than 90 percent of all bladder cancers fall into this category. There are subcategories of transitional cell carcinomas, depending on where the tumor is growing and how much the cancer has spread: - Superficial bladder cancer. When the cancer has stayed in the transitional layer and has not spread to the other layers of the bladder (the connective tissue, the muscles, and beyond), it’s called superficial bladder cancer, or carcinoma in situ. The recurrence rate for this type of cancer is high; it often comes back as another superficial bladder cancer after treatment. “The rate of recurrence for this type of cancer is 60 to 80 percent,” says Jeff Holzbeierlein, MD, associate professor at the University of Kansas Medical Center in Kansas City, Kan. “There are already changes in the lining of the bladder — cell changes have already occurred, so the cancer is still likely to come back.” - Invasive bladder cancer. When a superficial bladder cancer spreads to the deeper layers of the bladder wall, it is called invasive bladder cancer. Cancer that has spread to the muscle tissue and beyond is more serious than invasive cancer that has reached only the connective tissue. - Metastatic bladder cancer. Invasive bladder cancer can spread to nearby organs, such as the uterus or vagina in women and the prostate gland in men. It can enter the lymphatic system and blood vessels, and travel to the liver, lung, bones — any organ in the body. 2. Squamous cell carcinoma: This type of bladder cancer usually forms after a long-term infection, such as chronic urinary infections, or chronic irritation of the bladder, such as from bladder stones. These infections or irritations can cause transitional cells to change into squamous cells, which are thin, flat cells that are at greater risk of turning into cancer. 3. Adenocarcinoma: This is a rare but dangerous form of bladder cancer. Only 1 to 3 percent of all bladder cancers are this type, but the tumors tend to be aggressive. Adenocarcinoma can begin primarily in the bladder, but can also originate in the gland cells of other organs, like the lung, stomach, pancreas, liver, or colon, and then spread to the bladder. 4. Small cell bladder cancer: This is a rare form of bladder cancer, accounting for 1 to 2 percent of all bladder cancers. It can also originate elsewhere, such as in the lungs, and is a dangerous form of bladder cancer. “It’s usually metastatic (has spread outside of the bladder),” says Dr. Holzbeierlein. “We usually start with chemotherapy.” Bladder Cancer: Stage, Prognosis, and Recurrence Rates Once the type of bladder cancer has been determined, the doctor needs to determine how far the cancer has spread. This is called staging. Each stage of cancer has different survival rates. Stage 0 or I: The cancer is contained; the cancer cells have not grown beyond the inner lining of the bladder (Stage 0) or beyond the layer of tissue supporting the inner lining of the bladder (Stage I). The cancer has not extended into the muscle or out into lymph nodes. The five-year survival rate for Stage 0 bladder cancer is 95 percent while that for Stage I is 85 percent, according to the American Cancer Society. Stage II: The cancer cells have spread to the muscle layer; this stage of bladder cancer has a five-year survival rate of approximately 55 percent. Stage III: Cancer has spread outside the bladder to the fat separating the bladder from other organs, resulting in a five-year survival rate of 38 percent. Stage IV: Cancer cells have spread to other organs, reducing the five-year survival rate to 16 percent. Bladder cancer is a disease that has a high rate of recurrence, as much as 50 to 80 percent. Because of this high recurrence rate, follow-up for bladder cancer is especially important. Talk to your doctor about your individualized follow-up plan; most experts advise return visits and exams every three to six months. A diagnosis of bladder cancer can be daunting, but by learning about the types of bladder cancer and discussing the treatment and management options for your specific cancer with your doctor, you can arm yourself for battle against this often-treatable disease.
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