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Appendix (or appendiceal) cancer occurs when the appendix's cells mutate and grow out of control, forming a tumor. Tumors can either be malignant or benign (non-cancerous), but even benign tumors can sometimes transform and become malignant. Malignant appendix tumors can spread to other parts of the body, while benign tumors usually stay in the appendix.
Appendix cancer is diagnosed in approximately 3,000 Americans each year. The number of cases has been increasing recently, particularly in patients under age 50. About half of the cases are found when a person has surgery for acute appendicitis. Others are discovered when a mass is seen during a CT scan performed for an unrelated condition or when the tumor has progressed to the point where it causes swelling (distension) in the abdomen.
Since appendix cancer is rare, all patients with an appendix tumor should have their diagnostic tests formally reviewed and seek the advice of doctors who specialize in treating appendix cancer.
The outcome for appendix cancer depends on a number of factors. These include tumor size, tumor grade (how abnormal the tumor cells appear under the microscope), how deep in the appendix the tumor has spread and if the tumor has spread beyond the appendix.
Types of appendix cancer
Appendix cancer is classified into two main types:
- Neuroendocrine tumors (NETs)
- Appendiceal adenocarcinoma
Neuroendocrine tumors (NETs)
About half of appendix cancers are neuroendocrine tumors (also called carcinoid tumors.) These tumors arise in neuroendocrine cells, which receive signals from the nervous system and release hormones. Many NETs are slow-growing and may not require treatment. Tumors less than 2 centimeters are less likely to be malignant and spread. Larger tumors generally require more aggressive treatment.
These tumors begin in the lining of the appendix (epithelium.) They specifically affect glandular cells, which secrete bodily fluids. There are several categories of adenocarcinoma tumors, summarized below:
- Mucinous adenocarcinoma: The second most common type of appendix cancer is mucinous adenocarcinoma. Mucinous tumors originate in the lining of the appendix, and they are characterized by their secretion of mucin, the gelatinous protein component of mucus.
- Goblet cell tumors: Goblet cell tumors, or goblet cell adenocarcinomas, affect both neuroendocrine cells and goblet cells in the lining of the appendix.
- Colonic-type adenocarcinoma: These tumors are similar to those of colorectal cancer and cause many of the same symptoms. They tend to appear near the base of the appendix.
- Signet ring cell adenocarcinoma: This aggressive tumor occasionally develops in the appendix. Symptoms may arise quickly and require immediate medical evaluation. Signet ring cell adenocarcinoma is associated with poor outcomes, but new treatments are being developed.
Mucinous cystadenoma: These benign (non-cancerous) tumors develop in the lining of the appendix. Tumors are surgically removed. So long as the appendix remains intact, mucinous cystadenoma is unlikely to spread to other organs.
Pseudomyxoma peritonei: Appendix cancer, especially adenocarcinomas, can sometimes lead to a syndrome known as pseudomyxoma peritonei (PMP).
PMP is characterized by the presence and growth of tumor cells that produce mucin (a component of mucus) in the abdomen. The tumor cells may start in the appendix, but PMP can also come from the ovary or stomach. As the tumor develops and fills with mucus, it may rupture and spread mucus throughout the peritoneal cavity - the space between the internal organs and the inner lining of the abdomen. As mucinous tumor cells grow and accumulate, they press on other organs. This pressure can impair the body's digestive functions and lead to malnutrition or a blockage of the intestines.
Common symptoms of PMP include increasing abdominal size, abdominal pain or pressure, a feeling of fullness and enlarged ovaries in women.
While a direct cause of appendix cancer is not known, anything that increases the chance of getting appendix cancer is considered a risk factor. They include:
- Age: Appendix cancer is most commonly diagnosed in people over 50 but is becoming more common in people aged 40-49. It is rare in children.
- Gender: Women are more likely to develop NETs than men, including NETs in the appendix.
- Certain health conditions, such as atrophic gastritis, pernicious anemia or Zollinger-Ellison syndrome, which affect the stomach’s ability to make acid.
- Having a family history of multiple endocrine neoplasia type 1 (MEN1) syndrome (also called Wermer syndrome).
Not everyone with risk factors gets appendix cancer. However, if you have risk factors, you should discuss them with your doctor.
Learn more about appendix cancer:
Why choose MD Anderson for appendix cancer treatment?
When you are treated in MD Anderson’s Gastrointestinal Center for appendix cancer, some of the nation’s top experts focus on finding the best treatment for you. While few other centers have expertise in treating appendix cancer, MD Anderson has a dedicated team with clinical and research expertise in this disease.
MD Anderson’s multi-disciplinary tumor board consists of surgeons, medical oncologists, pathologists and radiologists with specific expertise in appendix cancer. The doctors from these different specialties work together closely and communicate often to be sure you receive the most advanced, personalized care with the fewest possible side effects.
Appendix cancer expertise
As one of the nation’s top-ranked cancer centers, MD Anderson treats a high volume of appendix cancer patients. This give our oncologists more experience than most.
Surgery is often the main therapy for cancer of the appendix, and the skill of the surgeon is an important part of your successful treatment. MD Anderson surgeons perform upwards of 100 hyperthermic intraperitoneal chemotherapy (HIPEC), or heated chemotherapy, procedures each year. This exceptional level of expertise gives you higher chances for successful treatment.
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Prevention & Screening
Many cancers can be prevented with lifestyle changes and regular screening.