What Is Appendix Cancer?
Understanding a Rare Cancer — Because Every Story Deserves Clarity, Care, and Support
Medically reviewed by John Paul Shen, MD, Department of Gastrointestinal Medical Oncology, The University of Texas MD Anderson Cancer Center, and APPENDICURE Board Member. Reviewed May 2026.
Appendix Cancer Explained
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 people 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. The behavior depends entirely on which type of appendix cancer 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 guidelines.
- 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 the 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 to those born in the 1940s.
Today, one in every three appendix cancer patients is diagnosed before age 50. For comparison, only 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 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 deeper detail on each, visit our Types of Appendix Cancer page.
Mucinous neoplasms (LAMN and HAMN) — Tumors that produce a thick jelly-like substance called mucin. LAMN (Low-grade Appendiceal Mucinous Neoplasm) grows slowly. HAMN (High-grade Appendiceal Mucinous Neoplasm) has more aggressive cellular features and was added as its own category in the 2019 World Health Organization classification.
Mucinous adenocarcinoma — A true cancer that produces mucin and invades the appendix wall. Roughly 40-50% of appendiceal adenocarcinomas are mucinous.
Non-mucinous (intestinal-type) adenocarcinoma — Behaves more like a colon cancer. About 30-35% of appendiceal adenocarcinomas.
Signet ring cell carcinoma — A rare and aggressive form, named for the ring-shaped appearance of the cancer cells under a microscope. About 4-5% of cases. Tends to spread early and requires intensive treatment.
Goblet cell adenocarcinoma — A distinctive tumor with features of both gland-forming cells and hormone-producing (neuroendocrine) cells. Often behaves more aggressively than a classic neuroendocrine tumor.
Neuroendocrine tumors (NETs / carcinoid tumors) — Start in the hormone-producing cells of the appendix. Most are small, slow-growing, and discovered incidentally during an appendectomy.
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 (G1) is typically associated with LAMN. High-grade PMP (G2) 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, as its symptoms often resemble more common conditions like appendicitis or digestive issues. This section outlines the key signs to watch for—such as abdominal pain, bloating, or unexpected changes in bowel habits—so patients and caregivers can better recognize when to seek medical evaluation. Understanding these symptoms may help prompt timely diagnosis and treatment.
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:
- 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.
- 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 have 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 Chair of ACPMP’s Medical Advisory Board, Dr. Laura Lambert, 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
Frequently Asked Questions
Is appendix cancer the same as colon cancer?
No. Although the appendix is attached to the large intestine, appendix cancer is a distinct disease with its own pathology, behavior, and treatment guidelines. Some non-mucinous appendiceal adenocarcinomas behave similarly to colon cancers, but most appendix cancers do not.
Is appendix cancer curable?
Many appendix cancers — especially small neuroendocrine tumors and LAMNs confined to the appendix — are highly curable with surgery alone. More aggressive types, or cancers that have spread to the peritoneum, often require multi-step treatment but can still be effectively managed at specialty centers. Outcomes vary significantly by type and stage.
How long does it take to get a diagnosis?
Because most appendix cancers are discovered incidentally after appendectomy, the initial diagnosis often comes days to weeks after the surgery, once pathology is complete. Full staging and treatment planning typically take an additional 2-6 weeks.
Does appendix cancer run in families?
For most patients, no clear hereditary cause has been identified. Some appendiceal tumors have molecular features overlapping with hereditary colorectal cancer syndromes, but appendix cancer is not classified as a familial cancer. Genetic counseling may be recommended in certain cases.
What is the difference between appendix cancer and pseudomyxoma peritonei?
Appendix cancer is the primary tumor. PMP is the condition that can develop when a mucin-producing appendix tumor leaks or ruptures into the abdomen. Not all appendix cancers cause PMP, and PMP can occasionally arise from other primary sites (such as the ovary), although the appendix is by far the most common origin.
What is HIPEC?
HIPEC stands for Hyperthermic Intraperitoneal Chemotherapy. It is a one-time treatment in which heated chemotherapy is circulated directly inside the abdomen during a surgery called cytoreductive surgery (CRS). It is used to treat peritoneal spread from appendix cancer and other abdominal cancers, and is performed at specialized centers.
Should I get a second opinion?
Yes. For a disease this rare, we strongly recommend a second opinion at a specialty center before starting treatment — even if you plan to ultimately receive care closer to home. Specialty pathologists also re-read slides more accurately for rare tumors.
Are there clinical trials for appendix cancer?
Yes, and the number is growing. ClinicalTrials.gov lists active trials, and ACPMP maintains a curated list of trials specifically for appendix cancer and PMP. Specialty centers can also help match you to appropriate studies.
Why is appendix cancer rising in younger adults?
The cause is not yet known. The 2025 Vanderbilt study confirmed the trend but did not identify why. Hypotheses under investigation include environmental exposures, dietary patterns, microbiome changes, and shared causes with the broader rise in early-onset gastrointestinal cancers.
What questions should I ask my doctor?
Bring a written list to every appointment. Start with: What exact type and grade is my tumor? Has my pathology been reviewed by a specialist in appendiceal disease? What is the stage? Do I need additional imaging? Would I benefit from CRS/HIPEC or systemic chemotherapy? Are there clinical trials I qualify for? Should I be seen at a specialty center?
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
- 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. Version 5.1.0.0.
- 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.
- MD Anderson Cancer Center, Gastrointestinal Medical Oncology.
About the Medical Reviewer
John Paul Shen, MD is an Assistant Professor in the Department of Gastrointestinal Medical Oncology at The University of Texas MD Anderson Cancer Center, where his research focuses on the molecular characterization of appendiceal cancer and the development of precision therapies for rare gastrointestinal cancers. Dr. Shen serves on the Board of APPENDICURE.
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.
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