Cancer is a disease in which cells grow in an abnormal way. Normally, cells divide in a controlled manner. If cells keep dividing when new cells are not needed, a mass of tissue called a tumor forms.
A tumor can be benign or malignant. A benign tumor is not cancer. It will not spread to other parts of the body. A malignant tumor is cancer. Cancer cells spread and cause damage around them. They can also enter the lymph and blood streams. This makes it easier to spread cancer to other parts of the body.
Normal Anatomy and the Development of Bladder Cancer
The urinary bladder is a hollow, muscular organ. It's found in the pelvis. The bladder has 4 layers of muscle. Urothelial cells line the inside of the bladder and urinary system. Urine made by the kidneys travels down tubes called ureters. Urine is stored in the bladder. Then, it’s passed from the body through the urethra. In females, the bladder is in front of the vagina. In males it’s in front of the rectum. Other structures surround the bladder. They can all be affected by cancer.
Cell division and cell death are normal. It’s meant to replace old or damaged cells. The inside lining of the bladder is a place where there may be a high rate of turnover. This is because it's exposed to waste products in the urine. Irritation of the bladder wall can be increased. This can happen with chronic conditions of the bladder and exposure to toxins.
Bladder cancer can cause bleeding or interfere with how the bladder works. If it grows beyond the bladder walls, the cancer can grow into nearby structures such as the rectum, vagina, or intestines. This will interfere with how they work. It can also spread to lymph nodes or blood vessels. They carry cancer to other sites in the body. The most common sites for bladder cancer to spread are the lymph nodes in other parts of the body, the bones, lungs, liver, and belly.
Types of Bladder Cancer
Almost all bladder cancers are transitional cell carcinomas. This type of cancer starts and grows in the deepest layer. This layer is made of urothelial or (transitional) cells.
The 2 types are:
- Papillary
—Finger-like projections that grow from the surface of the bladder wall into the open space of the bladder. They generally don't grow into the deeper layers of the bladder wall.
- Flat
—They are flat and line the inner layer of the bladder.
Bladder cancer is described by how invasive the tumor is. In situ, or non-muscle invasive cancer, is only found in local tissue. This means the cancer is contained a certain place and has not spread. It's the easiest to treat and offers the best chance for a cure. Muscle invasive cancers spread into the muscle layers. If the cancer has been growing for a long time, it can grow deeper and spread to other parts of the body.
Other types of bladder cancer are also classified by the tissue they start in. These types are:
- Squamous cell carcinoma
—Flat cells found on the inner wall. This type of cancer is almost always invasive.
- Adenocarcinoma
—Cells that form in the glandular tissue. This type of cancer is almost always invasive.
- Small cell carcinoma
—Rare and arise from nerve cells in the glands. This type of cancer grows fast, but can be treated.
- Sarcoma
—Very rare and arise from the muscular tissue of the bladder.
