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 are described below.

Colonic-type adenocarcinoma

This accounts for 10 percent of appendix cancers. 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

Also called MAA for short, this type happens in females and males equally, typically around 60 years old.

MAA is further classified as either:

  • low grade
  • high grade

Goblet cell adenocarcinoma

Goblet cell adenocarcinoma is also called GCA. It’s rare, accounting for just up to 19 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

In this type, sometimes known as typical carcinoid, a tumor forms with certain cells from the wall of the bowel.

It accounts for about half of all appendix cancers. It can metastasize, or spread, but can be successfully treated with surgery.

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.

Appendix cancer may not have any noticeable symptoms in the beginning. 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 may not occur until the cancer is more advanced.

While some experts state that there are no established risk factors for developing appendix cancer, a few potential ones have been suggested.

These include:

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

The treatment for appendix cancer depends on the:

  • type of tumor
  • stage of the cancer
  • person’s overall health

Surgery is the most common treatment for localized appendix cancer. If the cancer is localized to the appendix only, then the treatment is usually to remove the appendix. This is also called an appendectomy.

For some types of appendix cancer, or if the 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.

If the cancer has spread, then your doctor may recommend cytoreductive surgery, also called debulking. In this type of surgery, the surgeon will remove the tumor, surrounding fluid, and possibly any nearby organs that are attached to the tumor.

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

Types of chemotherapy include:

  • systemic chemotherapy, given intravenously or by mouth
  • regional chemotherapy, given directly into the abdomen, such as intraperitoneal chemotherapy (EPIC) or hyperthermic intraperitoneal chemotherapy (HIPEC)
  • a combination of systemic and regional chemotherapies

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

According to a 2011 review, 5-year survival rates for appendix cancer after the appendix was removed are:

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

The 5-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 early stage appendix cancer.

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