Bladder cancer types

Bladder cancer is categorized by a number of types, depending on where exactly it forms, along with other factors. The most common type of bladder cancer is transitional cell (urothelial) carcinoma (TCC). This type accounts for about 95 percent of bladder cancers. Cancer cells of this type look like the urothelial cells lining the inside of the bladder.

Subtypes of the most common type of bladder cancer

There are two subtypes of TCC, outlined below.

Papillary carcinoma: Grows out from the inner surface of the bladder toward the hollow center in finger-like projections. Often, these tumors are called noninvasive papillary cancers, meaning they don’t grow into the deeper layers of the bladder wall. When papillary TCC is very low grade, it may be called papillary neoplasm of low-malignant potential, and these bladder cancer treatments typically have positive outcomes.

Flat carcinomas: This type of TCC does not grow out of the urothelium toward the center of the bladder. Rather, flat carcinomas remain on the surface of the bladder wall. If a flat carcinoma is confined to the urothelium, it is called noninvasive flat carcinoma or flat carcinoma in situ.

Other bladder cancer terms

Bladder cancer may also be described in terms of how invasive the cancer is, or how deep into the bladder wall it has grown.

Noninvasive bladder cancer: The cancer cells are found only in the innermost layer of the cells of the bladder, called the transitional epithelium. The cancer hasn’t yet grown any deeper than this first layer.

Invasive bladder cancer: The cancer cells have grown beyond the first layer of the bladder wall. Invasive bladder cancer may be more challenging to treat and may continue to spread. Invasive bladder cancer may also be described as muscle-invasive bladder cancer once it reaches the muscles in the bladder wall.

Another way to describe bladder cancer is based on how far it’s generally spread and whether it’s returned after initial diagnosis and treatment.

Recurrent bladder cancer: Cancer is recurrent when it comes back after treatment. Fast-growing but noninvasive bladder cancer has a higher likelihood of returning after treatment. Speak with the cancer care team about treatment options designed to lower the risk of recurrence.

Metastatic bladder cancer: Advanced bladder cancer has spread, or metastasized, to distant sites in the body. This makes the cancer harder to treat, and the treatment plan may be focused on reducing the effects of the tumor, shrinking its size or reducing treatment side effects.

Rare types of bladder cancer

Rarer forms of bladder cancer include those listed below.

Squamous cell carcinoma accounts for about 1 percent to 2 percent of bladder cancers diagnosed in the United States, according to the American Cancer Society (ACS). Squamous cells look similar to the flat cells on the surface of the skin. Almost all squamous cell carcinomas of the bladder are invasive.

Adenocarcinoma of the bladder closely resembles the gland-forming cells seen in colon cancers, and accounts for about 1 percent of bladder cancers in the United States, the ACS notes.

Small-cell carcinoma is extremely rare, accounting for fewer than 1 percent of all bladder cancers diagnosed in the United States, according to the ACS. This type of bladder cancer begins in neuroendocrine cells, which are similar to nerves.

Sarcoma is another very rare type of bladder cancer that begins in the muscle layer of the bladder wall.

Next topic: What are the stages of bladder cancer?