Types of Bladder Cancer

November 25, 2024

This page was reviewed under our medical and editorial policy by Kevin G. Chan, M.D., clinical professor, division of urology and urologic oncology, Department of Surgery, City of Hope^® Cancer Center Duarte

During the bladder cancer diagnosis process, the care team may assign a bladder cancer type based on the type of cell in which the cancer developed.

A pathologist (a doctor specializing in disease identification using tissue analysis) examines a sample of tumor cells under a microscope to determine the cell type. This tissue sample is obtained from a biopsy (a procedure to remove a small amount of tissue from the body), and it helps doctors provide an accurate diagnosis.

Additional characteristics are used to help doctors identify bladder cancer treatment options. These characteristics address how the condition grows and spreads, allowing doctors to identify the disease stage and how aggressive the cancer is.

Urothelial Carcinoma

Urothelial carcinoma accounts for the vast majority of bladder cancer cases in the United States, about 90%. It is sometimes called transitional cell carcinoma (TCC) because the urothelial cells from which it develops are also known as transitional cells. This is because they may expand when the bladder is full and contract when it is empty.

These urothelial (transitional) cells line the bladder and, as more cancer cells grow, they may form a cancerous tumor.

Urothelial cells also line other parts of the urinary tract, such as the urethra (the tube that carries urine from the bladder out of the body), ureter (the tube connecting the bladder to the kidneys) and renal pelvis (the kidney’s center, which collects urine and channels it to the ureter). If doctors suspect that a person has urothelial bladder cancer, they will check for cancer in these areas as well.

Less Common Types of Bladder Cancer

In addition to urothelial carcinoma, there are also less common bladder cancer types. These include the following.

Squamous cell carcinoma: This type of cancer develops in squamous cells. These are flat, thin cells that form from transitional cells due to long-term irritation or inflammation, such as from an infection. In the U.S., squamous cell carcinoma accounts for an estimated 4% of bladder cancer diagnoses.

Small cell carcinoma: Cells that receive signals from the nervous system and release hormones in response are known as neuroendocrine cells. Small cell carcinoma of the bladder develops in these cells. It is an aggressive form of bladder cancer, meaning it tends to grow and spread quickly. It is also rare, accounting for less than 1% of bladder cancers.

Sarcoma: Sarcoma cancer of the bladder is also rare. It develops in the muscle or fat layers of the bladder. One type of bladder sarcoma is known as rhabdomyosarcoma (RMS), which develops in the skeletal muscles (muscles that people control to move the body).

Adenocarcinoma: About 2% of bladder cancers are adenocarcinomas. This type of bladder cancer develops in glandular cells that make fluids such as mucus.

Other Characteristics of Bladder Cancer

Bladder cancer is also characterized by how it grows and how far it has spread (metastasized). This information helps doctors recommend treatment options.

The bladder wall has several layers. Most bladder cancers begin in the innermost layer, the transitional epithelium (urothelium). As the cancer grows through deeper layers (the connective tissue, muscle and fatty layers), it becomes more advanced and its stage (the amount of and spread of cancer) is higher.

Some tumors may grow through these deeper layers to reach nearby tissues and lymph nodes, and eventually organs and bones, throughout the body. Other cancers may stay in the transitional epithelium permanently, or for a time.

Muscle-Invasive Versus Non-Muscle-Invasive

Non-invasive bladder cancer is the classification doctors use to describe the disease when it has not spread beyond the transitional epithelium. This is also referred to as Stage 0 cancer or carcinoma in situ (CIS).

Invasive bladder cancers are those that have spread beyond the transitional epithelium to other bladder layers. This is Stage 1, Stage 2, Stage 3 or Stage 4 bladder cancer.

If bladder cancer has spread beyond the transitional epithelium, but not beyond the connective tissue layer (lamina propria), it is known as non-muscle-invasive. This is Stage 1 bladder cancer.

If the disease has reached the muscle of the bladder wall or into the fatty layer, surrounding tissues or other organs, it is known as muscle-invasive. This is Stage 2, Stage 3 or Stage 4 bladder cancer.

Papillary Versus Flat

Bladder cancer also has two ways of growing, depending on its subtype.

Papillary: This subtype has projections that look like fingers, which extend from the transitional epithelium (inner bladder wall layer) into the hollow bladder center. It typically, though not always, grows inward like this, rather than through the other bladder wall layers.

Flat: This subtype is also located in the transitional epithelium, but it does not extend into the bladder center. Flat carcinoma of the bladder is, however, considered an aggressive cancer because of its tendency to grow into other bladder wall layers. It is sometimes called Stage 0is, flat carcinoma in situ or flat, non-invasive carcinoma.

Flat or papillary bladder carcinoma that does begin to grow through the bladder wall layers becomes urothelial (transitional cell) carcinoma.