Appendiceal Cancer: A Plain-Language Guide

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 gut lining. Most tumors of this kind cause mucin to build up. That buildup can make the appendix burst.

Neuroendocrine tumors of the appendix start in a different cell. Enterochromaffin cells release chemicals that control digestion and gut movement. These tumors are also called carcinoid tumors. NCI says they are the most common cancer of the appendix.

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.

For neuroendocrine tumors of the appendix, NCI's clinician summary gives clear size cutoffs. They decide whether you need a second, bigger surgery.

About 90% of these tumors are smaller than 1 cm. They also sit away from the base of the appendix. NCI states that these can be consistently cured by appendectomy alone. Nothing more is needed.

Tumors larger than 2 cm are handled differently. NCI says they require a right-sided hemicolectomy, which removes the right part of the colon, plus removal of nearby lymph nodes. The risk of spread is too high to leave alone.

Between 1 and 2 cm, NCI calls the decision controversial. The bigger surgery may be right if the tumor has grown into the mesoappendix, the fold of tissue that holds the appendix. It may also be right if tumor was left at the cut edge, or if lymph nodes hold cancer. Some teams also weigh the Ki-67 index, a measure of how fast cells divide. NCI notes the evidence behind those cutoffs is limited.

If you had an appendix removed and are now told you need more surgery, ask for the tumor size in centimeters. That number is the reason.

On the epithelial side, mucinous tumors are graded by how the cells look. Low grade is written LAMN. High grade is written HAMN.

When the appendix bursts, mucin spills into the belly. It keeps building up there. That condition is called pseudomyxoma peritonei, shortened to PMP.

This is not the usual kind of spread through the blood. It is physical spread of mucin-making cells across the lining of the abdomen. That is why the main sign is often a slowly swelling belly rather than pain.

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.

Goblet cell carcinoid, also called adenocarcinoid, is a rare mix of both cell types. NCI describes it as aggressive. It shows up around age 50. It often looks like an inflamed appendix at first, and it tends to spread to the peritoneum and the ovaries.

One detail is easy to miss. Goblet cell tumors do not carry somatostatin receptors. So an indium In 111-octreotide scan cannot see them. If that scan was ordered on the assumption this is an ordinary carcinoid, the assumption needs checking.

NCI describes treatment as right hemicolectomy with lymph node removal, plus chemotherapy. For widespread disease, surgery may include peritonectomy and removal of the ovaries.

NCI notes that many people have no symptoms early. Later signs include pain, bloating, a growing belly, a lump, nausea and vomiting, or feeling full after a few bites.

Most diagnoses are accidents. 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.

Biopsy of the appendix itself is very hard to do. NCI says samples are usually taken instead from tissue where the cancer may have spread. A camera can also be placed into the belly through a small cut. That procedure lets doctors look at the peritoneum and sample it.

Surgery removes the appendix. It may also remove parts of the intestine, colon, and peritoneum.

When disease has spread across the abdomen, NCI describes a different approach. Heated chemotherapy is washed through the abdominal cavity during the operation. It is called HIPEC, short for hyperthermic intraperitoneal chemotherapy.

This is not the same as chemotherapy through a vein. It is done at centers that perform it often. Asking a surgeon how many of these operations the team does each year 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.

The clinician summary is blunter about the extremes. Survival is excellent while the tumor stays local. With distant spread, 10-year survival is about 30%. Across gut neuroendocrine tumors in general, case series put 5-year survival at 39% to 60% once metastases are present.

How rare is rare? NCI has put appendiceal cancer at roughly 1 to 2 people per million per year in the United States. It notes recent studies show the number is rising. Most cases appear between ages 50 and 55, though it can happen at any age. Neuroendocrine tumors of the appendix tend to strike younger people than other tumors here. 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.
• You vomit and pass no stool or gas. That can mean a blockage, and it needs same-day care.

• 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