Appendix Cancer
Appendix cancer is a rare type of cancer that begins when cells in the appendix grow out of control. The appendix is a small pouch attached to the first part of the large intestine. Because appendix cancer is so uncommon, many people only find out they have it after having surgery to remove the appendix to treat appendicitis. But they find out that what their healthcare professionals thought was appendicitis was really appendix cancer. Appendix cancer is sometimes called appendiceal carcinoma or appendiceal cancer.
There are several types of appendix cancer, and each one behaves differently. Some types grow very slowly and may stay in the appendix for years. Others can spread more quickly to the lining of the abdomen or to other organs. How serious it is depends on the cancer type, how far it has spread, and how the cells look under a microscope.
Slow-growing, low-grade appendix cancers can often be cured with surgery. But more-aggressive ones may need additional treatment, such as traditional chemotherapy or a specialized procedure called hyperthermic intraperitoneal chemotherapy (HIPEC).
Even though appendix cancer is still very rare — affecting only about 1 to 2 people per 100,000 each year — it has been diagnosed more often in recent years, including in younger adults. Many people live for years after diagnosis, especially when the cancer is found early or can be completely removed with surgery.
Appendix cancer can begin in different kinds of cells inside the appendix. These cancers are broadly grouped into two main types: epithelial appendix cancers and neuroendocrine appendix cancers. Each behaves differently and may require different treatments.
Epithelial appendix cancers
Epithelial cancers start in the cells that line the inside of the appendix. These cells typically help make a jellylike fluid, called mucus, that protects the lining of the digestive tract. When these tumors grow, many produce large amounts of mucus. If the appendix ruptures or leaks, this mucus can spread through the abdomen and cause a condition called pseudomyxoma peritonei (PMP).
Epithelial appendix cancers include a few subtypes:
- Adenocarcinomas. These cancers start from the gland cells that line the appendix. There are two main types: mucinous and nonmucinous. Nonmucinous type also is called colonic type. Adenocarcinomas are often treated with a more extensive surgery, such as removing part of the colon.
- Appendiceal mucinous neoplasms (AMNs). These tumors make a jellylike fluid called mucus. AMNs can be low-grade (LAMN) or high-grade (HAMN). LAMN tumors grow slowly, while HAMN tumors are more likely to spread.
- Goblet cell adenocarcinomas. These rare tumors have features of both gland-forming and hormone-producing cells. They tend to grow faster than neuroendocrine tumors and often need more-extensive surgery and sometimes chemotherapy.
- Signet ring cell carcinomas. This is a rare and aggressive type of adenocarcinoma. The cancer cells look like rings under a microscope and tend to spread early. These usually require intensive treatment.
Neuroendocrine appendix cancers
Neuroendocrine tumors (NETs), sometimes called carcinoid tumors, start in hormone-producing cells. These cells help regulate digestion. NETs are the most common type of appendix tumor and are often found unexpectedly after surgery for suspected appendicitis. Many NETs grow slowly and can be treated successfully by removing the appendix. Larger tumors or those that involve lymph nodes may require additional treatment and follow-up.
Appendix cancer can be hard to detect because many people don’t have symptoms at first. In fact, it’s often found by accident during surgery for appendicitis or another abdominal problem. When symptoms do appear, they can be mild and easy to mistake for other conditions.
If the cancer grows larger, symptoms may include:
- Pain in the lower right side of the belly. This is the same area where appendicitis pain usually happens.
- A growing belly size caused by mucus or fluid buildup inside the abdomen, which may happen with mucinous tumors or a condition called pseudomyxoma peritonei.
- Nausea or vomiting.
- Feeling full soon after you eat.
When to see a doctor
Because these symptoms can be caused by many other health problems, it’s important to talk with a healthcare professional if symptoms last more than a few days or seem unusual for you. Early evaluation and imaging can help find the cause and, if needed, guide treatment.
Medical experts don’t yet know the exact cause of appendix cancer. It happens when healthy cells in the appendix begin to change and grow in ways they shouldn’t. Over time, these cells can form a tumor.
Researchers believe these changes may begin in the DNA inside cells, but the reason this happens is still not clear. Unlike some cancers, appendix cancer has no known lifestyle or environmental cause.
In most people, appendix cancer seems to occur by chance. It’s important to remember that nothing you did or didn’t do caused it. Scientists continue to study why certain appendix cells become cancerous and how to detect these changes early.
Although the cause of appendix cancer isn’t known in most cases, research shows some associations with older age and inherited genetic variations. These factors do not guarantee that someone will develop appendix cancer. They merely highlight areas where risk might be slightly higher. Because this cancer is so rare and understudied, definitive risk factor profiles are not yet established.
Appendix cancer can lead to problems in the belly and other parts of the body, especially if it spreads or causes a buildup of mucus or fluid. Some possible complications include:
- Pseudomyxoma peritonei (PMP). Some appendix tumors make a jellylike mucus that can leak into the abdomen. This mucus can fill the belly and put pressure on the organs, leading to bloating, discomfort or trouble eating.
- Spread of cancer, called metastasis. If the cancer moves to other areas — such as the lining of the abdomen, ovaries or liver — it can cause new symptoms such as swelling, weight loss or fatigue.
These complications can typically be treated or managed. Regular follow-up and imaging help healthcare professionals find and address problems early.
Appendix cancer is difficult to diagnose early because it usually doesn’t cause clear or specific symptoms. The appendix is a small organ tucked deep in the lower right side of the abdomen, so small tumors can grow there for a long time without being noticed. Many people learn they have cancer only after surgery for appendicitis or another abdominal condition.
If a healthcare professional suspects appendix cancer, several steps can help make the diagnosis:
- Medical history and exam. Your health professional usually asks about your symptoms, family history and any past health problems. During the exam, typically your abdomen is examined for swelling or tenderness.
- Imaging tests. Computerized tomography (CT) or MRI scans create detailed pictures of your abdomen and pelvis to look for tumors, fluid buildup or signs that the cancer has spread. Ultrasound can sometimes detect an enlarged appendix or fluid, especially when appendicitis is suspected.
- Surgery and biopsy. The most common way appendix cancer is found is during surgery to remove the appendix, called an appendectomy. After surgery, a pathologist examines the tissue under a microscope to see if cancer cells are present and to determine the exact type and grade.
- Lab and genetic tests. Blood tests may be used to check levels of chemicals made by cancer cells, called tumor markers. This can help medical professionals track treatment or recurrence. Some people also may benefit from genetic testing if there’s a family history of cancer or if the tumor type suggests an inherited risk.
Each of these steps helps your care team understand the exact type and stage of your cancer so your care team can create the best treatment plan for you.
Treatment for appendix cancer depends on the type of tumor, how advanced it is, and your overall health. Your care team will design a plan that’s right for you.
The main treatment options include:
Surgery or other procedures
Surgery is the main treatment for most types of appendix cancer. The goal is to remove the tumor and any nearby tissue where cancer cells may have spread. The exact type of surgery depends on the tumor’s size, location and whether it has spread beyond the appendix.
- Appendectomy. If the cancer is small and limited to the appendix, removing the appendix alone may be enough. This is often the case for slow-growing tumors such as neuroendocrine tumors (NETs) or low-grade mucinous neoplasms (LAMNs).
- Right hemicolectomy. If the tumor is larger, high-grade or near the base of the appendix, surgeons may remove part of the colon and nearby lymph nodes to make sure all the cancer is gone.
- Cytoreductive surgery (CRS). When appendix cancer has spread throughout the abdomen, surgeons perform a special operation to remove as much visible cancer as possible. Even if all the cancer can’t be removed, this helps other treatments work better. During the surgery, the surgeon may remove tumors from the lining of the abdomen, called the peritoneum, and sometimes parts of nearby organs. CRS is sometimes called debulking surgery. This procedure is often followed by a specialized treatment called hyperthermic intraperitoneal chemotherapy (HIPEC).
Therapies
In addition to surgery, some people with appendix cancer benefit from treatments that use medicine to destroy or control cancer cells. These therapies include:
- Hyperthermic intraperitoneal chemotherapy (HIPEC). HIPEC is a specialized cancer treatment used for cancers that have spread to the lining of the abdominal cavity, known as the peritoneum. CRS is typically done before HIPEC. After CRS, the abdominal cavity is bathed with heated chemotherapy medicine to target any remaining microscopic cancer cells. This combined approach can significantly reduce the risk of cancer recurrence, improve survival rates and even offer a potential cure for some people.
- Traditional chemotherapy. Chemotherapy treats cancer with strong medicines. For advanced or high-grade cancers that have spread beyond the abdomen, chemotherapy given through a vein may help shrink or slow the cancer.
Targeted therapy or immunotherapy. For some people with advanced cancer or for those who are not able to have CRS, doctors may recommend medicines that target specific changes in the cancer or help the immune system attack it. These options include treatments that block tumor blood vessel growth, called antiangiogenesis therapy. It may also involve immunotherapy for tumors with certain genetic features.
These therapies are based on early studies in appendix cancer and research from other digestive system cancers. These therapies are typically only used in specialized centers or clinical trials.
Surveillance
For some slow-growing or completely removed tumors, your healthcare professional may recommend regular checkups and scans instead of immediate further treatment.
There is a higher risk of colon cancer in people with appendiceal tumors, so a colonoscopy is recommended if one has not been done recently.
References
- Rossi A, et al. Appendiceal neoplasms — A practical guide. Journal of Surgical Oncology. 2023; doi:10.1002/jso.27304.
- Godfrey EL, et al. Consensus guideline for the management of patients with appendiceal tumors, part 1: Appendiceal tumors without peritoneal involvement. Cancer. 2025; doi:10.1002/cncr.35867.
- Chmiel A, et al. Treatment and management of peritoneal spread from appendiceal neoplasms. Surgical Oncology Clinics of North America. 2025; doi:10.1016/j.soc.2024.10.001.
- Holowatyj AN, et al. Inherited cancer susceptibility gene sequence variations among patients with appendix cancer. JAMA Oncology. 2022; doi:10.1001/jamaoncol.2022.5425.
- Janczewski LM, et al. Survival outcomes used to validate version 9 of the American Joint Committee on Cancer staging system for appendiceal cancer. CA: A Cancer Journal for Clinicians. 2023; doi:10.3322/caac.21806.
- AJCC Cancer Staging System. American College of Surgeons; 2025. https://www.facs.org/quality-programs/cancer-programs/american-joint-committee-on-cancer/cancer-staging-systems/. Accessed Nov. 18, 2025.
- Clancy TE, et al. Well-differentiated neuroendocrine tumors of the appendix. https://www.uptodate.com/contents/search. Accessed Nov. 18, 2025.
- Seivastava A, et al., eds. Non-neoplastic and neoplastic disorders of the appendix. In: Gastrointestinal and Liver Pathology: Foundations in Diagnostic Pathology. 3rd ed. Elsevier; 2024. https://www.clinicalkey.com. Accessed Nov. 18, 2025.
- Appendiceal cancer. National Cancer Institute. https://www.cancer.gov/pediatric-adult-rare-tumor/rare-tumors/rare-digestive-system-tumors/appendiceal-cancer. Accessed Dec. 4, 2025.
- Gastrointestinal neuroendocrine tumor early detection, diagnosis, and staging. American Cancer Society. https://www.cancer.org/cancer/types/gastrointestinal-carcinoid-tumor/detection-diagnosis-staging.html. Accessed Dec. 4, 2025.
- Godfrey EL, et al. Consensus guideline for the management of patients with appendiceal tumors, part 2: Appendiceal tumors with peritoneal involvement. Cancer. 2025; doi:10.1002/cncr.35874.
- Wang D, et al. Incidence trends and survival analysis of appendiceal tumors in the United States: Primarily changes in appendiceal neuroendocrine tumors. PLOS One. 2023; doi:10.1371/journal.pone.0294153.
- Appendiceal neoplasms and cancers. National Comprehensive Cancer Network. https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1546. Accessed Nov. 18, 2025.
- Medical review (expert opinion). Mayo Clinic. Dec. 12, 2025.
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