Development of malignant (irregular/harmful) cells that originate from the bladder is called bladder cancer. Most bladder cancers start in the urothelium or the transitional cell layer. There are four subtypes of bladder cancer: Transitional Cell Carcinoma, Squamous Cell Carcinoma, Adenocarcinoma, and Small Cell Carcinoma. Transitional Cell Carcinoma is the most common type of bladder cancer.
These same types of cancer can also grow in other places in the urinary tract, such as the lining of the kidney (called the renal pelvis), the ureters, and the urethra. In fact, patients with bladder cancer sometimes have a similar tumor in the lining of the kidneys, ureters, or urethra. Therefore, when someone is found to have a cancer in one part of their urinary system, the entire urinary tract needs to be checked for tumors.
Transitional cell (urothelial) carcinoma
This is the most common type of bladder cancer. About 95% of bladder cancers are this type. The cells from transitional cell carcinomas look like the urothelial cells that line the inside of the bladder. Transitional cell carcinomas are also divided into 2 subtypes, papillary and flat.
Papillary carcinomas grow in slender, finger-like projections from the inner surface of the bladder toward the hollow center. Papillary tumors often grow toward the center of the bladder without growing into the deeper bladder layers. These tumors are called non-invasive papillary cancers. Very low-grade non-invasive papillary cancer is sometimes calledpapillary neoplasm of low-malignant potential and tends to have a very good outcome.
Flat carcinomas do not grow toward the hollow part of the bladder at all. If a flat tumor is only in the inner layer of bladder cells, it is known as a non-invasive flat carcinoma or aflat carcinoma in situ (CIS).
If either a papillary or flat tumor grows into deeper layers of the bladder, it is called an invasive transitional cell (or urothelial) carcinoma. Two very important traits in predicting the outlook for transitional cell carcinomas are the grade of the cancer and whether or not it is invasive.
Grade: These tumors are divided into grades based on how abnormal the cells look under a microscope. If the cells look more like normal cells, the cancer is called a low-grade cancer. When the cells look more abnormal, the cancer is high-grade. Lower-grade cancers tend to grow more slowly and have a better outcome than higher-grade cancers.
Invasiveness: If the cancer stays in the mucosal layer of bladder without growing into the deeper layers, it is called non-invasive. If the cancer grows into the lamina propria or even deeper into the muscle layer, it is called invasive. Invasive cancers are more likely to spread and are harder to treat. You may also see a bladder cancer described as superficial or non-muscle invasive. These terms describe tumors that have not grown into the main muscle layer of the bladder.
Squamous cell carcinoma
In the United States, only about 1% to 2% of bladder cancers are squamous cell carcinomas. Under a microscope, the cells look much like the flat cells that are found on the surface of the skin. Nearly all squamous cell carcinomas are invasive.
Only about 1% of bladder cancers are adenocarcinomas. These cancer cells have a lot in common with gland-forming cells of colon cancers. Nearly all adenocarcinomas of the bladder are invasive.
Less than 1% of bladder cancers are small-cell carcinomas, which start in nerve-like cells called neuroendocrine cells. These cancers typically need to be treated with chemotherapy similar to that used for small-cell carcinoma of the lung.
Cancers rarely start in the muscle cells of the bladder. But when they do, these cancers are called sarcoma in adults and Rhabdomyosarcoma in children.
Most common symptoms of bladder cancer are blood in the urine, urgency of urination, pain over the bladder area, frequency of urination, and burning with urination. One must note that many of the symptoms are also found in urinary conditions such as urinary tract infection; enlarged prostate in men, pelvic prolapse in women, urinary stones, and other problems. Therefore, seeking evaluation with a skilled urologist is important in determining the exact cause of the symptoms.