What is Appendix Cancer?

Understanding a rare cancer, because every story deserves clarity, care, and support.

Medically reviewed by appendix cancer specialists. Reviewed May 2026.

If you or someone you love just heard the words “appendix cancer,” you are probably reading this in a strange in-between place. The diagnosis is too new to fully understand. The Google searches are turning up confusing terms. The friends and family asking how you’re doing have no idea what to say, because most of them have never heard of this disease.

We’ve been there. APPENDICURE was built by patients, caregivers, and survivors, not a hospital marketing department, to give you what we wish someone had handed us on day one: clear answers, real information, and the reassurance that you are not navigating this alone.

This page is the place to start.

What appendix cancer actually is

Appendix cancer, also called appendiceal cancer, is a rare disease in which abnormal cells grow inside the appendix, a small, finger-shaped organ that hangs off the lower right side of the large intestine. For a long time the appendix was dismissed as a useless leftover from human evolution. We now believe it plays a role in the immune system and may act as a reservoir for healthy gut bacteria.

When something goes wrong inside the appendix at the cellular level, the result can be a benign growth, a borderline neoplasm, or a true cancer. What happens next depends almost entirely on which type of appendix tumor it is, and there are several.

A few facts that often surprise people:

• Appendix cancer is not stomach cancer, colon cancer, or ovarian cancer, even though it can look like any of them on imaging or under a microscope. It is its own disease with its own behavior and its own treatment pathways.
• It rarely causes obvious symptoms early on. Most cases are discovered by accident, during surgery for what looks like ordinary appendicitis.
• It is rare, but it is rising. And the rise is happening in a generation that almost no one expected.

How rare is it, really?

For decades, oncologists described appendix cancer as affecting roughly 1 to 2 people per million in the United States each year, about 3,000 new cases nationwide. That number alone made it one of the rarest cancers in medicine.

But in June 2025, a research team led by Dr. Andreana Holowatyj at Vanderbilt University Medical Center published a study in Annals of Internal Medicine that changed the conversation. Using the National Cancer Institute’s SEER database, they tracked appendix cancer incidence from 1975 through 2019 and found something striking: rates have more than tripled in people born in the late 1970s and quadrupled in people born in the 1980s, compared with those born in the 1940s.

Today, roughly one in three appendix cancer patients is diagnosed before age 50. For comparison, only about one in eight colorectal cancer patients is diagnosed that young.

Researchers do not yet know why. The rise is unlikely to be explained by better detection, there is no standard screening test for appendix cancer. Possible explanations under investigation include environmental exposures, dietary changes, and shifts in gut microbiome health, but no single cause has been confirmed.

What this means for you: if you are reading this as a younger adult who was just diagnosed, you are not an anomaly. You are part of a trend the medical community is only beginning to understand.

The main types of appendix cancer

The single most important thing to learn early is which type of appendix tumor you have. Treatment, prognosis, and follow-up all depend on it. The pathology report from your surgery (or biopsy) will name the type. If you don’t have it yet, ask for a copy, you are entitled to it, and you will refer back to it often.

Here are the main categories, in plain language. For a deeper walkthrough of each, including how they behave, how they’re treated, and what the latest expert consensus says, visit our Types of Appendix Cancer page.

LAMN, Low-grade Appendiceal Mucinous Neoplasm. A slow-growing tumor that produces a thick, jelly-like substance called mucin. LAMNs are not technically classified as cancer, but they can rupture and spread mucin into the abdomen, which has long-term implications.

HAMN, High-grade Appendiceal Mucinous Neoplasm. Similar to LAMN but with more aggressive cellular features. HAMN was formally recognized as its own category in the 2019 World Health Organization classification.

Appendiceal Adenocarcinoma (AA). A true cancer arising from the lining of the appendix. AA includes several subtypes, the most aggressive of which is signet ring cell carcinoma, named for the ring-shaped appearance of the cancer cells under a microscope, and treated as a high-grade subtype rather than a standalone disease.

Goblet Cell Adenocarcinoma (GCA). A distinctive tumor with features of both gland-forming and hormone-producing cells. The older term “goblet cell carcinoid” is no longer used; current classification treats GCA as a form of adenocarcinoma with its own grading system.

Neuroendocrine Tumors (NETs) and MiNENs. Tumors arising from the hormone-producing cells of the appendix. Most NETs are small, slow-growing, and discovered incidentally during an appendectomy. MiNEN (Mixed Neuroendocrine–Non-neuroendocrine Neoplasm) is a less common mixed tumor.

Note: The terminology above reflects the Godfrey 2025 Cancer consensus guidelines from the Peritoneal Surface Malignancies Consortium, which APPENDICURE uses as its primary clinical reference. We explain why in detail on our Types of Appendix Cancer page.

What is PMP, and why does everyone keep mentioning it?

If you spend any time in the appendix cancer community, you will hear the term PMP, Pseudomyxoma Peritonei, within your first week.

PMP is not a separate cancer. It is a clinical condition that can develop when a mucin-producing appendix tumor leaks or ruptures, releasing mucin (and sometimes tumor cells) into the abdominal cavity. Over time, this mucin can coat the surfaces of organs in the abdomen.

PMP is graded by how aggressive the cells inside the mucin appear. Low-grade PMP is typically associated with LAMN. High-grade PMP is more often associated with HAMN or mucinous adenocarcinoma and is harder to treat.

Treatment of PMP typically involves a specialized surgery called cytoreductive surgery (CRS), often combined with heated chemotherapy delivered directly into the abdomen, HIPEC (Hyperthermic Intraperitoneal Chemotherapy). Our webinar with Dr. Laura Lambert (below) explains how this works in patient-friendly terms.

Signs & Symptoms

Appendix cancer can be difficult to detect early. Its symptoms often look like more common conditions, appendicitis, irritable bowel, a stomach bug, even ovarian issues in women. This is part of why so many cases are found by accident.

The signs to know:

Why these symptoms are so easy to miss

There is no routine screening for appendix cancer. No blood test. No imaging test. No colonoscopy equivalent. The symptoms above overlap with dozens of common, harmless conditions, which is why most appendix cancers are discovered one of two ways:

1. Incidentally during appendectomy. A patient goes to the ER with what looks like appendicitis. Surgeons remove the appendix. The pathologist examines it under a microscope and finds tumor cells. Many patients learn they have cancer days or weeks after their surgery.
2. During unrelated imaging or surgery. A scan for back pain, an ovarian mass workup, or an unrelated abdominal procedure reveals something abnormal in or around the appendix.

If you’ve had appendicitis-like symptoms that didn’t resolve normally, or you’ve been told you had a “complicated” appendix, ask whether the appendix was sent to pathology and what the report showed. You are entitled to a copy of that report.

Watch and Learn

Mike Mullaney with Mix 104.1 New England Lifestyles Radio interviews Dr. Laura Lambert, Chair of ACPMP’s Medical Advisory Board, about appendix cancer.

Alia Poulos, MA, MPP, University of Chicago Medicine Comprehensive Cancer Center, Office of Community Engagement.

What Happens After Diagnosis

Once an appendix tumor is identified, the next steps usually include:

• A complete pathology review to confirm the type and grade. Many patients benefit from having their slides reviewed by a pathologist who specializes in appendix tumors.
• Staging imaging, typically a CT scan of the chest, abdomen, and pelvis to look for any signs of spread.
• Tumor marker bloodwork, CEA, CA 19-9, and CA-125 are sometimes elevated in appendix cancer and are used to track disease over time.
• A consultation with a surgical oncologist experienced in appendiceal disease.

Treatment options depend entirely on type, stage, and whether the disease has spread to the peritoneum. They can range from observation (for many small LAMNs) to right hemicolectomy (removal of part of the colon), CRS/HIPEC, systemic chemotherapy, and clinical trial enrollment. For a full walkthrough, see our Diagnosis and Treatment page.

Where You Go Matters

This is the most important sentence on this page: appendix cancer outcomes depend significantly on where you are treated.

Because appendix cancer is rare, many community oncologists and general surgeons will see only one or two cases in their entire careers. Specialized centers, sometimes called Centers of Excellence, see hundreds. They have dedicated pathologists, surgeons trained in CRS/HIPEC, oncologists familiar with the specific drug regimens that work for appendix cancer subtypes, and ongoing clinical trials.

If you take only one action after reading this page, make it this one: get a second opinion at a specialty center before beginning treatment. Even if you ultimately receive treatment closer to home, the staging plan, surgical approach, and follow-up regimen will benefit from input from a team that sees this disease every week instead of every few years.

Our Medical Centers & Providers page lists specialty centers where appendix cancer is treated regularly.

You Are Not Alone

When we built APPENDICURE, we did it for one reason: the resources we needed when we were newly diagnosed did not exist in one place. Patient stories were scattered. Medical information was either too technical or too generic.

You can:

• Join our private Appendicure Facebook community of patients, caregivers, and survivors
• Read Patient & Caregiver Stories from people who have walked this path
• Attend our Webinars featuring specialists from MD Anderson, Yale, and other leading centers
• Browse curated Web Resources including ACPMP, NORD, and PMP Pals
• Consider joining the APPENDICURE Patient-Led Data Registry, which contributes anonymized patient experience data to accelerate research

Sources and References

• Holowatyj AN, et al. Birth Cohort Effects in Appendiceal Adenocarcinoma Incidence Across the United States. Annals of Internal Medicine. 2025. Vanderbilt University Medical Center summary
• Godfrey TC, et al. Diagnosis and management of appendiceal neoplasms, Parts 1 and 2: Consensus guidelines from the Peritoneal Surface Malignancies Consortium. Cancer. 2025.
• Shen JP, et al. Evaluation of Adjuvant Chemotherapy in Patients With Low-Grade Mucinous Appendiceal Adenocarcinoma. JAMA Network Open. 2023.
• World Health Organization Classification of Tumours, 5th Edition: Digestive System Tumours. 2019.
• College of American Pathologists. Protocol for the Examination of Specimens From Patients With Carcinoma of the Appendix.
• Peritoneal Surface Oncology Group International (PSOGI) Consensus Guidelines.
• National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) Program.
• American Cancer Society. Cancer Facts & Figures 2026.

The content provided on the APPENDICURE website is intended for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. We encourage readers to consult qualified healthcare providers to discuss any medical concerns.