The type of gallbladder cancer depends on the kind of cell where it began. Several varieties of cells in the gallbladder develop different gallbladder cancer types. Pathologists (doctors who specialize in diagnosing disease) can identify the type of gallbladder cancer by looking at tumor cells under a microscope.

Gallbladder Adenocarcinoma

Most gallbladder cancer — about 90 percent — is adenocarcinoma. This growth begins in the glandlike cells that line the insides of the gallbladder. There are three types of adenocarcinoma of the gallbladder:

• nonpapillary adenocarcinoma
• papillary adenocarcinoma
• mucinous adenocarcinoma

Nonpapillary adenocarcinoma is the most common.

Papillary adenocarcinoma is rare and less likely to spread to the liver and nearby lymph nodes. People with this type of gallbladder cancer have a better outlook than most people with a gallbladder adenocarcinoma.

Mucinous adenocarcinoma is even rarer. It begins in the cells that produce mucin, the primary ingredient of mucus.

Other Gallbladder Types

Other types of gallbladder cancer are quite rare. They include:

• adenosquamous carcinoma
• squamous cell carcinoma
• carcinosarcoma

These begin in different types of cells in the gallbladder. They are often more aggressive than adenocarcinoma of the gallbladder.