The appendix is a tube that looks like a small sack or pouch. It’s connected to the colon near the beginning of the large intestine. The appendix doesn’t have a known purpose. However, it may have something to do with the immune system.

Appendix cancer is sometimes called appendiceal cancer. It occurs when healthy cells become abnormal and grow rapidly. These cancerous cells become a mass or tumor inside the appendix. When the tumor is malignant, it’s considered cancerous.

Appendix cancer is considered very rare. In the United States, there are about 1.2 cases of appendix cancer per 100,000 people each year, according to a 2015 review.

There are different classifications of appendix cancers that aren’t well-defined. The lack of well-defined classifications is due to the rarity of this type of cancer, which limits the amount of research. The broad classifications of appendix cancer usually include:

Colonic-type adenocarcinoma

This is the most common type of appendix cancer. It’s similar to colon cancer in look and behavior. It usually appears in people between the ages of 62 and 65, and is more common in men than women.

Mucinous adenocarcinoma of the appendix

This is also called MAA. It has two types: a low grade and a high grade.

Goblet cell adenocarcinoma

This is also called GCA. It’s rare, accounting for less than 20 percent of all cases of appendix cancer in the United States. It involves the presence of intestinal-type goblet cells. Goblet cells reside in the intestinal and respiratory tract.

Neuroendocrine carcinoma

This is also known as typical carcinoid. In this type, a tumor forms with certain cells from the wall of the bowel. It accounts for about half of all appendix cancers, according to the American Society of Clinical Oncology. It usually doesn’t metastasize, or spread.

Signet ring cell adenocarcinoma

This may be considered a subtype of colonic-type adenocarcinoma or mucinous adenocarcinoma. While it’s the most aggressive type and most likely to spread to other organs, it’s very rare. This type more commonly occurs in the colon or stomach, but can develop in the appendix as well.

Most of the time, appendix cancer doesn’t have any noticeable symptoms. It’s usually discovered during surgery or during an imaging test for another condition like appendicitis. Your doctor may also discover it during a routine colonoscopy. However, if there are symptoms, they may include:

Many of these symptoms don’t occur until the cancer has reached an advanced stage and spread to other organs.

Specific risk factors haven’t been established for appendix cancer. However, there are some common factors that may be considered potential risk factors. These possible risk factors vary slightly for each classification of appendix cancer. The possible risk factors for the main types are as follows:

Colonic-type adenocarcinoma

  • age: approximately 62 to 65
  • sex: more males than females

Mucinous adenocarcinoma of the appendix

  • age: approximately 60

Goblet cell adenocarcinoma

  • age: early 50s
  • possible association with schistosomiasis, a disease resulting from an infection of parasitic worms

Neuroendocrine carcinoma

  • age: approximately 38 to 48
  • sex: slightly more females than males
  • ethnicity: seems to be more common in Caucasians and African-Americans

Health conditions that may increase your risk for appendix cancer may include:

  • pernicious anemia, a deficiency of vitamin B-12
  • atrophic gastritis, or long-term inflammation of stomach lining
  • Zollinger-Ellison syndrome, a condition of the digestive tract
  • family history of multiple endocrine neoplasia type 1 (MEN1), a disorder that leads to tumors in the glands that produce hormones
  • smoking

There’s currently not a risk factor that shows that appendix cancer itself is hereditary.

The most common treatment for appendix cancer is surgery. This surgery is usually to remove the appendix. This is also called an appendectomy.

For some types of appendix cancer, or if your tumor is larger, your doctor may recommend removing one half of your colon and also some lymph nodes. Surgery to remove half of your colon is called a hemicolectomy.

Treatment may include chemotherapy before or after surgery if:

  • the tumor is larger than 2 centimeters
  • the cancer has spread, especially to the lymph nodes
  • the cancer is more aggressive

Afterward, your doctor will follow up with imaging tests, such as a CT scan or MRI, to ensure the tumor is gone.

The recurrence rate is low for early stage and less aggressive forms of appendix cancer. The survival rate for appendix cancer is high. In many cases, removing the appendix with the tumor contained inside is all the treatment you’ll require.

According to a 2011 review, five-year survival rates for appendix cancer after removal of the appendix are:

  • 94 percent if the carcinoid tumor is confined to the appendix
  • 85 percent if the cancer has spread to regional, or close, organs
  • 34 percent if the cancer has spread to distant organs, but this is very rare for carcinoid tumors

The five-year survival rate increases for some cases of appendix cancer when part of the colon is also removed and chemotherapy is used. However, not all cases of appendix cancer require these additional treatments.

The survival rate and outlook are generally good for most people with appendix cancer. Treatment often only requires removal of the appendix.

In most cases, appendix cancer goes undetected until an appendectomy is already being performed for other reasons. However, after any cancer diagnosis, it’s important to follow up regularly with your doctor to be sure there’s no recurrence of cancer.