The urinary bladder is a part of the urinary system. It is a muscular, hollow organ that stores the urine produced by the kidneys. Several types of cells are present in the bladder. These include urothelial cells, squamous cells, and epithelial cells. Abnormal growth and division in one or more of these bladder cells result in tumor formation, and this condition is known as bladder cancer or bladder tumor. A bladder tumor most commonly occurs in the cells present in the internal lining of the bladder. In most cases, this cancer type is diagnosed in the early stages, and therefore, the treatment outcomes are usually good.
Men have a higher chance of developing urinary bladder cancer than women. It has been reported that the lifetime chances in men for developing bladder tumors are 1 in 28, while in women, it is 1 in 91. Bladder carcinoma ranks sixth in the list of most common cancers in men and seventeenth in the list of most common cancers in women.
The common types of bladder cancer are:
Urothelial bladder carcinoma was previously called transitional carcinoma. It is the most common form of bladder cancer and accounts for 90% of all bladder carcinomas. It initiates in the urothelial cells. These cells form the internal lining of the urinary bladder. Urothelial cells are also present at other sites of the urinary tract, such as urethra and ureters. People with urothelial cancer may have tumors at these sites, and therefore, doctors usually examine the complete urinary tract in patients.
Squamous cells are flat, thin cells present on the lining of the bladder. Squamous cell carcinoma of the bladder includes about 5% of all bladder carcinomas. People with chronic inflammation or bladder irritation have a higher risk for squamous cell carcinoma of the bladder. Squamous cell carcinoma is more prevalent in geographic areas where parasite-associated bladder infections (schistosomiasis) are common.
This is a rare type of bladder carcinoma, and it forms in the neuroendocrine cells. They account for less than 2% of all bladder carcinomas. This cancer generally grows rapidly and should be promptly treated with chemotherapy.
Adenocarcinoma of the bladder is a rare cancer that accounts for 1 to 2% of all bladder carcinomas. Adenocarcinoma develops in the mucus-secreting glandular cells of the urinary bladder. Patients with chronic inflammation or irritation of the urinary bladder have a higher risk of developing adenocarcinoma.
Sarcoma in the bladder initiates in the muscular wall of the bladder. It is a rare cancer of the urinary bladder.
It includes carcinoma in situ and non-invasive papillary carcinoma. Non-invasive papillary carcinoma does not grow into deeper layers, and it can be easily removed. Carcinoma in situ grows only on or near the bladder surface.
Non-muscle-invasive bladder lesion does not grow into the muscle but affects the lamina propria.
Muscle-invasive bladder lesions grow into the muscles and sometimes spread to fatty tissues.
The urinary bladder cancer staging is as follows:
It is divided into two stages - stage 0a and stage 0is. Stage 0a is noninvasive papillary carcinoma. It may be low-grade or high-grade, depending on the characteristics of the cancer cells under the microscope. Stage 0is is carcinoma in situ, and in most cases, it is a high-grade tumor characterized by a flat tumor on the inner lining of the bladder.
In stage 1 bladder cancer, the cancer invades the connective tissue below the inner lining of the urinary bladder. The cancer has not spread to the muscle wall of the bladder. Further, the cancer has not spread to the nearby lymph nodes or distant organs.
In stage 2 bladder cancer, the cancer spreads through the connective tissue and invades the muscular wall. However, it has not completely invaded the muscle layer to reach the fatty tissue present below it. Further, the cancer has not spread to the nearby lymph nodes or distant organs.
Stage 3 bladder cancer is divided into stages 3a and 3b. In stage 3a of bladder carcinoma, the cancer has completely invaded the muscle layer and reached the fatty layer surrounding the bladder. The cancer may also have spread to the prostate and seminal vesicles in men or to the vagina and uterus in women. However, it has not reached the abdominal wall, lymph nodes, or distant organs. In stage 3b bladder carcinoma, the cancer has invaded the lining, muscular wall, connective tissue, and fatty tissues and spread to >2 lymph nodes.
Stage 4 bladder cancer is divided into two sub-stages. Stage 4a bladder carcinoma has invaded the abdominal wall and the pelvis. However, it may or may not have spread to the lymph nodes. It may not have spread to distant organs. Stage 4b bladder carcinoma may or may not have invaded the nearby abdominal cavity organs and lymph nodes. It has spread to one or more distant organs, such as the lungs, bones, and liver.
Bladder cancer is a form of cancer that develops in the urinary bladder. The different types of bladder cancer include squamous cell carcinoma, urothelial carcinoma, small cell carcinoma, and adenocarcinoma. Stage 0 and stage 1 bladder cancers are categorized as early-stage or initial-stage cancers, and stage 4 bladder cancer is referred to as advanced-stage cancer.