Overview

The appendix is a pouch-like tube that is attached to the cecum (the first section of the large intestine or colon). The appendix averages 10 centimeters (cm) in length and is considered part of the gastrointestinal (GI) tract. Generally thought to have no significant function in the body, the appendix may be a part of the lymphatic, exocrine, or endocrine systems.

Appendix cancer occurs when cells in the appendix become abnormal and multiply without control. These cells form a growth of tissue, called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). Another name for this type of cancer is appendiceal cancer.

Types of appendix tumors

There are a variety of tumors that can start in the appendix, including:

Carcinoid tumor. A carcinoid tumor starts in the hormone-producing cells that are normally present in small amounts in almost every organ in the body. A carcinoid tumor arises primarily in either the GI tract or lungs, but it also may occur in the pancreas, testicles (men), or ovaries (women). An appendix carcinoid tumor most often occurs at the tip of the appendix. Approximately 66% of all appendix tumors are carcinoid tumors. This type of cancer usually causes no symptoms until it has spread to other organs, and often goes unnoticed until it is found during an examination or procedure performed for another reason. An appendix carcinoid tumor that remains confined to the area where it started has a high chance of successful treatment with surgery. For more information, see the Guide to Carcinoid Tumor.

Mucinous cystadenocarcinoma. Mucinous cystadenocarcinoma is the most common non-carcinoid appendix tumor and accounts for approximately 20% of appendix cancer cases. This type of tumor produces a jelly-like substance called mucin that fills the abdominal cavity and can cause abdominal pain, bloating, and changes in bowel function.

Colonic-type adenocarcinoma. Colonic-type adenocarcinoma accounts for approximately 10% of appendix tumors and usually occurs at the base of the appendix. This type of tumor looks and behaves similarly to the most common type of colorectal cancer. It often goes unnoticed, and diagnosis is frequently made during or after surgery for appendicitis (inflammation of the appendix that can cause abdominal pain or swelling, loss of appetite, nausea, vomiting, constipation or diarrhea, inability to pass gas, or a low fever that begins after other symptoms).

Signet-ring cell adenocarcinoma. Signet-ring cell adenocarcinoma (so called because under the microscope, the cell looks like it has a signet ring inside it) is very rare and considered to be more aggressive and more difficult to treat than other types of adenocarcinomas. This type of tumor usually occurs in the stomach or colon, and can cause appendicitis when it develops in the appendix.

Paraganglioma. Paraganglioma is a rare tumor that develops from cells of the paraganglia, a collection of cells that come from nerve tissue that remains in small deposits after fetal (pre-birth) development, and is found near the adrenal glands and some blood vessels and nerves. This type of tumor is usually considered benign and is often successfully treated with the complete surgical removal of the tumor. Paraganglioma is very rare outside of the head and neck region.

Statistics

Primary appendix cancer (cancer that starts in the appendix) is uncommon, and statistics for appendix cancer are typically included as part of colorectal cancer data. It is estimated that about 1% of colorectal cancer cases in the United States are primary appendix cancer, affecting about 1,500 people each year.

The overall five-year relative survival rate (percentage of people who survive at least five years after the cancer is detected, excluding those who die from other diseases) of people with appendix cancer varies depending on several factors, including the type of tumor. If the tumor can be removed with surgery and is localized to the appendix, the five-year survival rate is 70% to 90%. If the cancer has spread outside of the appendix, most patients survive two years.

Cancer survival statistics should be interpreted with caution. It is not possible to tell a person how long he or she will live with appendix cancer. Because the survival statistics are measured in five-year intervals, they may not represent advances made in the treatment or diagnosis of this cancer.

Source: The National Cancer Institute.

Find out more about basic cancer terms used in this section.