There are many different types of anal cancer. Many of these cancers are similar to the types of cancer found in the vagina, urethra, and bladder. Some of these tumors are benign, or non-cancerous. Often these tumors are treated in the same manner as anal cancer because they can turn into cancer in time. Warts, skin tags, and small flaps of skin that hang loose from the body are considered benign tumors as well. There are 5 different types of anal cancer that could appear on the anus.

Squamous Cell Carcinoma

This type of anal cancer is by far the most common in the United States, representing 80% of all cases of anal cancer. This type of cancer begins in the lower part of the anus. It is most often found in the anal canal but could also be found on the anal verge. The lining of the anus and the skin of the anus is composed primarily of squamous cells. Squamous cells are flat and plate-shaped and form connective tissues in the body. During the earliest stages of development, it is known as a carcinoma in situ (CIS) meaning that the malignant growth has yet to penetrate deep into the squamous cells of the anal lining. Carcinoma in situ is a type of precancerous tumor. When the tumor grows deeper into the tissue, it is then considered invasive. There is one subtype of squamous cell carcinoma, it is called cloacogenic carcinoma because its origins begin in a part of the anus called the cloaca.

Adenocarcinoma

Some anal cancers start in the glands found near the anus. This type of cancer is known as adenocarcinoma. Paget disease is a type of adenocarcinoma that found on the anus that originates in the subcutaneous glands near the anus and eventually manifests as a tumor on the skin's surface. This cancer is not to be confused with the bone disease of the same name.

Skin Cancers

Skin cancers can be found in the anal region as well. Only about 1 percent of all anal cancers are some type of skin cancer due to lack of UV radiation on the anus. Basel cell melanomas are extremely rare on the anus. Melanomas are slightly more common and can be dangerous because they can resemble hemorrhoids, inducing a potentially fatal misdiagnosis. Most anal melanomas are diagnosed in late stages as a result.

Gastrointestinal stoma tumors

Gastrointestinal stoma tumors are more commonly found on the stomach or the intestines. They rarely manifest as a type of anal cancer. When these tumors are found at an early stage, they can easily be surgically removed. In the case that they are found at a later stage, they are more often treated with drugs.