The type of bladder cancer is based on how the cancer cells look under a microscope. To make a diagnosis, a pathologist looks at the tumor cells. A pathologist is a doctor who diagnoses disease using a microscope.

Non-muscle invasive bladder cancer (NMIBC) stays in the bladder’s inner linings. Muscle invasive bladder cancer means the cancer is in the muscle of the bladder.

NMIBC and Urothelial Carcinoma of the Bladder

About 9 out of 10 bladder cancers are urothelial carcinoma (also called transitional cell carcinoma). They start in the cells on the surface of the bladder’s inner linings. Most urothelial carcinomas are a form of non-muscle invasive bladder cancer (NMIBC). That means the tumor stays within the bladder’s inner lining.

Urothelial carcinoma also has rarer subtypes, called variants. Each one has a different treatment. We identify the variant based on how the cells look under a microscope. The variants are called:

• Plasmacytoid
• Nested
• Micropapillary
• Lipoid cell
• Sarcomatoid
• Microcystic
• Lymphoepithelioma-like
• Inverted papilloma-like
• Clear cell

MSK’s bladder cancer experts are very experienced in diagnosing and treating bladder cancer. This includes non-muscle invasive and muscle invasive bladder cancer, and rarer forms of urothelial bladder carcinoma.

Urothelial carcinoma (yoo-REE-thrul KAR-sih-NOH-muh) is by far the most common type of bladder cancer in the United States. Others are rarer. This section has information on some of these rarer types. Some rare bladder cancers are more common outside of the United States.

Squamous Cell Carcinoma of the Bladder

This cancer begins in the thin, flat squamous cells that can form in the bladder after chronic inflammation (swelling) and infection. It’s most often found in areas, such as the Middle East, where a parasitic infection called schistosomiasis is common. In North America and Europe, squamous cell carcinoma is the second most common bladder cancer. It accounts for about 5 out of every 100 cases.

Adenocarcinoma of the Bladder

This rare form of bladder cancer accounts for about 1 out of every 100 cases of the disease. denocarcinoma (A-deh-noh- KAR-sih-NOH-muh) can be caused by certain bladder problems you’re born with. It’s also caused by chronic infection and inflammation.

Small Cell Carcinoma of the Bladder

This form of the disease can spread very quickly. It’s often, but not always, found at an advanced stage, after it has metastasized (spread). Small cell bladder cancers usually need a combination of treatments, including chemotherapy, surgery, and radiation therapy.

Small cell carcinoma starts in small, nerve-like cells in the bladder called neuroendocrine (NOOR-oh-EN-doh-krin) cells. It makes up about 1 out of every 100 cases of bladder cancers.