Appendiceal Cancer: A Plain-Language Guide

This page is for people who have been told they have a tumor of the appendix, and for their families. It explains the main types, how they are found and treated, and what the numbers mean.

The appendix is a small pouch of tissue at the start of the large intestine. NCI is candid that we do not know what it does. It may help the immune system.

What matters is that two unrelated cancers grow there. They share almost nothing except an address.

Epithelial appendiceal cancer, also called adenocarcinoma, starts in the cells that line the appendix. Those cells make mucin, a jelly-like substance that protects the digestive tract lining. Most epithelial tumors can cause mucin to build up. That buildup can make the appendix rupture.

Neuroendocrine tumors of the appendix start in a different kind of cell. NCI says they are the most common type of appendiceal cancer.

The two behave so differently that a general article about "appendix cancer" can mislead you. Find the exact tumor name on the pathology report first. Pathology reports shows where to look.

NCI's rare-tumor page and its treatment summaries describe surgery to remove the appendix. Some people also have surgery to remove the right side of the colon, along with nearby lymph nodes. Whether you need the bigger operation depends on the tumor type and how far it has grown.

Tumor size, grade, and the margins (the edge of the removed tissue) all matter. If you had an appendix removed and are now told you need more surgery, ask your surgeon to explain why. Ask for the tumor size and margin status in writing.

NCI notes that most appendiceal neuroendocrine tumors are small when found and rarely spread.

On the epithelial side, mucin can build up. When the appendix ruptures, mucin spills into the belly and keeps building up there. NCI links this to a condition called pseudomyxoma peritonei, shortened to PMP.

NCI notes that this cancer usually spreads straight into the abdomen when the appendix ruptures. Spread through lymph nodes to sites outside the abdomen is less common.

Appendiceal tumors come in other, rarer forms. The exact name on your pathology report matters, so ask your team to explain it.

NCI notes that many people have no symptoms early. Later signs include:

• pain
• bloating
• a growing belly
• a lump
• nausea and vomiting
• feeling full after a few bites

Most diagnoses are found by accident. The appendix comes out for suspected appendicitis. Then the pathologist finds cancer in it. Others turn up on a scan done for some other reason.

NCI says biopsies of the appendix are very difficult to do. Samples are usually taken instead from tissue where the cancer may have spread. NCI also lists diagnostic laparoscopy, which uses an instrument placed in the abdomen to view the organs.

Surgery removes the appendix. It may also remove other tissue in the abdomen.

For spread inside the abdomen, NCI describes using hot chemicals to wash the inside of the abdomen during surgery. This is often called HIPEC, short for hyperthermic intraperitoneal chemotherapy.

This is not the same as chemotherapy through a vein. Asking a surgeon how much experience the team has with this operation is fair. Getting a second opinion covers how to raise it.

NCI gives a 5-year survival rate of 67% to 97% for appendiceal neuroendocrine tumors and other low-grade tumors. Rates for advanced or spread disease are much lower. NCI adds an unusual warning: so few people have this cancer that these rates may not be very accurate.

NCI's treatment summary says that for gut neuroendocrine tumors in general, having metastases is linked to a drop in 5-year survival of 39% to 60%. That figure is not specific to the appendix.

How rare is rare? NCI puts appendiceal cancer at about 1 or 2 people per million per year. It notes recent studies show the number is rising. It is more common between ages 50 and 55, though it can happen at any age. Neuroendocrine tumors covers the wider family.

NCI states that appendiceal cancer is not known to run in families.

• Your belly is measurably larger, your waistband no longer fastens, or you gain several pounds without eating more. Mucin or fluid may be collecting.
• You feel full after a few bites for more than a few days.
• You had an appendectomy, the report mentions a tumor, and no follow-up was arranged. Ask for the size in centimeters and the margin status.

Do not wait a week if you vomit and pass no stool or gas, or have severe belly pain. That can mean a blockage. Get care right away, and call 911 if you cannot reach your team or feel very unwell.

• https://www.cancer.gov/pediatric-adult-rare-tumor/rare-tumors/rare-digestive-system-tumors/appendiceal-cancer
• https://www.cancer.gov/types/gi-carcinoid-tumors/hp/gi-carcinoid-treatment-pdq
• https://www.cancer.gov/types/gi-carcinoid-tumors/patient/gi-carcinoid-treatment-pdq