Appendix Cancer

Appendix cancer is a very rare cancer; 1 or 2 people in every 1 million are diagnosed. Appendix cancers make up less than 1% of all GI cancers. But like many other GI cancers, the rates are increasing, especially in young adults. Appendix cancer is often caught in later stages, once it has spread to nearby organs. For this reason, it can be aggressive and hard to treat. Appendiceal cancer is considered an "orphaned disease,” meaning there are not currently any FDA-approved drugs for its specific use. For the first time, in 2025, the National Comprehensive Cancer Network (NCCN) established provider guidelines for treating appendiceal neoplasms and cancers.

What is appendix cancer?

The appendix is located in the lower right area of the abdomen. It looks like a finger and sticks out from the colon. Its purpose is still being researched, however it may play a role in the immune system.

Appendix cancer forms in the cells lining the appendix and grows outward as it spreads. There are several types of appendix cancer, and treatment plans are customized based on what type of cells have become cancerous and how they’re behaving.  

Pseudomyxoma peritonei

A syndrome known as pseudomyxoma peritonei (PMP) often accompanies appendix cancer. A signature of PMP is tumor cells that produce mucin (a jelly-like substance) in the abdomen. The tumor cells may start in the appendix, but PMP can also come from an ovary or the stomach. PMP can increase your abdominal size, create pain or pressure, or give you an “I ate too much” feeling. Sometimes these symptoms are what lead to the discovery of appendix cancer.  

Types of appendix cancer

The histologic grade (also called “grade”) of appendix cancer is very important. This measures how aggressive the cancer is. Grades fall within low-grade (slow-growing cancers that are typically non-invasive and do not respond well to chemotherapy) and high-grade (fast-growing cancers that are invasive and may be more responsive to chemotherapy). 

In addition to the grade, these tumors may also be described by their “differentiation,” which describes normal or abnormal cells and whether or not they contain mucin, a jelly-like substance.

There are several types of appendix cancer:

Mucinous appendiceal neoplasms (LAMN/HAMN)

These tumors are not necessarily cancerous, but they pose a cancer risk if their mucin carries tumor cells and it leaks outside the appendix.

Appendiceal adenocarcinoma

This begins in the lining of the appendix. Tumors usually produce mucin. Subsets include:

Signet ring cell carcinoma (SRCC)

This is rare and tends to be more aggressive, it may spread to lymph nodes and/or the peritoneum inside of the abdomen.

Goblet cell adenocarcinoma (GCA)

GCA has features of adenocarcinomas and carcinoids; this is more aggressive than carcinoids but not as aggressive as poorly differentiated or SRCC.

Carcinoid, also known as neuroendocrine tumors (NET)

This makes up about half of all appendix cancers. Neuroendocrine tumors can appear in multiple places throughout the GI tract, including the appendix. These cancers need to be treated differently than adenocarcinomas. 

Read more about neuroendocrine cancer.

Staging appendix cancer

If you have appendix cancer, your treatment plan will be formed based on the type of cancer and your stage. Staging appendix cancer is complex because there are many factors and variables.

Appendiceal adenocarcinomas (SRCC and GCA) are staged on a scale from 0-4 (researchers use roman numerals 0-IV) based on the TNM staging system. In general:

• Stage 0 (carcinoma in situ): Cancer is in one spot and has not spread anywhere else.
• Stage 1: Cancer is confined to the inner layers of the appendix.
• Stage 2: Cancer has grown into connective or fatty tissue, to the outer layers of the appendix, and/or into the colon or rectum, but not to lymph nodes or distant organs.
• Stage 3: Cancer has grown into lymph nodes
• Stage 4 (also called “metastatic”): Cancer has spread to the abdomen and possibly other organs like the lungs; it may or may not be in lymph nodes.

What causes appendix cancer?

Risk factors put you at a higher risk of getting cancer. Some risk factors can be controlled with lifestyle changes, and others cannot. Older age, smoking, and obesity increase your risk of many cancers.

Just because you have a risk factor, that doesn’t mean you will get cancer. 

Most of the risk factors for appendix cancer are unknown; however these factors have been linked to cases: 

• Some studies suggest chronic use of antacids 
• Certain genetic diseases: familial adenomatous polyposis (FAP), Lynch syndrome, and multiple endocrine neoplasia type 1 (MEN1) syndrome 
• Personal history of GI tumors
• Family history of appendix cancer
• Low stomach acid (hypochlorhydria) 

Preventing appendix cancer

There are not any known ways to prevent appendix cancer. Researchers are still learning about what causes it.

As with every cancer, there are steps you can take to adopt a healthy lifestyle and reduce your overall cancer risk, such as maintaining a healthy weight, not smoking, and limiting or eliminating alcohol. 
Learn more about cancer prevention from the American Institute for Cancer Research.

How common is appendix cancer? 

Appendix cancer is a rare disease.

The NCI estimates that less than 1,000 people are diagnosed in the U.S. each year. However, a Vanderbilt study estimates that the true number of cases may be closer to 3,000 people per year.

1 in every 3 patients is diagnosed under the age of 50, however most people diagnosed are in their 50s. It’s found in both men and women, but women are more likely to develop NET.

Research published in the Annals of Internal Medicine found that the amount of patients with appendix cancer more than tripled for those born between 1976 to 1984, and quadrupled for those born between 1981 to 1989.

What are my odds of surviving it?

Because there are so few cases, survival statistics may not be accurate. However, the NCI currently states:

• 67-97% of patients with NET or other low-grade tumors are alive five years after diagnosis
• The survival rate for advanced appendiceal cancers can be much lower, as these cancers are harder to treat. 

What types of tests should I expect to undergo?

Appendix cancer is challenging to find in its earliest stages, because it often has few symptoms. It’s often found when a patient is being seen for appendicitis or undergoing surgery for a different problem. 

Doctors may use these tests to find and diagnose appendix cancer:

• Physical exam
• Imaging (CT, MRI, ultrasound, PET scan)
• Blood tests
• Urine tests
• Diagnostic Laparoscopy
• Scopes (like a colonoscopy)
• Biopsy

Ask your doctor about these additional tests—ideally before you begin treatment.

• Biomarker testing
• Genetic testing

I’m facing a diagnosis: What are my next steps?

If you’re facing a diagnosis, the GI Cancers Alliance is here for you. 

If you’re newly diagnosed, work with your doctor to create a treatment plan. 

It’s important to find an expert who specializes in appendiceal cancer. The top experts running clinical trials are looking into the molecular differences between colon cancer and appendix cancer. Although closely related, these two cancer types have shown different responses to treatment in clinical trials.

Surgical Centers of Excellence are often good places to start when making a treatment plan, as surgery (and possibly HIPEC) is often the first step in treating appendix cancer. You will need a multi-disciplinary team with oncologists, surgeons, and pathologists.

Most appendix cancer treatment plans include:

• Surgery (usually appendectomy, hemicolectomy, or cytoreductive (debulking))
• Chemotherapy (HIPEC may be recommended)
• Clinical trials (that may involve targeted therapy or immunotherapy)
• Radiation (less commonly used)

We strongly encourage you to get a second opinion from another trusted doctor so you feel confident moving forward.