The following is provided for informational purposes only. It is not medical advice. Your diagnosis, medical questions, and treatment plan are issues to be handled directly with your doctor.
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What is Appendix Cancer?
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Appendix cancer is cancer that starts in the cells lining the inside of the appendix. There a number of different types of cancers of the appendix. The different types are determined by which type of cells in the appendix become cancerous and what the cells look like under the microscope. The different types are associated with different behaviors (i.e. likelihood of spreading to other organs or other parts of the body, rate of growth, ability to be completely removed with surgery etc.) and therefore the types of treatment that are offered. Appendix cancers are the most common cause of pseudomyxoma peritonei (or “PMP”) (see below).
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What are the different types of Appendix Cancer?
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• Low grade mucinous neoplasms of the appendix (formerly known as mucinous cystadenomas) are non-cancerous tumors of the appendix. This means that they do not have any potential to spread to lymph nodes or through the blood stream to other organs. However, due to the flimsy nature of the appendix wall, if the appendix ruptures or the tumor grows through the wall, neoplastic cells may spread in the abdominal cavity, because the tumors are created by mucin-producing cells that line the inside of the appendix, and a mucinous substance (a gelatinous material) may accumulate in the abdomen. The build-up of mucin (also known as pseudomyxoma peritonei or PMP) can eventually lead to abdominal pain, bloating, and/or bowel obstructions.
• Adenocarcinomas are cancerous tumors created by gland-forming cells that line the inside of the appendix. They are also frequently mucin-producing cells and can result in accumulated mucin or PMP in the abdomen, but may also spread to other parts of the body, other organs in the abdomen or to the local lymph nodes. Adenocarcinomas are usually graded based on their microscopic appearance as either low-, moderate – or high-grade tumors. They can also be categorized by their differentiation (meaning how closely they resemble a normal cell). Well-differentiated and low-grade cancers tend to be slower growing and less likely to spread to other part of the body compared with high-grade or poorly-differentiated adenocarcinomas.
• Signet-ring cell adenocarcinomas (so called because of the physical appearance of the cells under the microscope) are a subset of adenocarcinomas of the appendix. Signet ring cell cancers are generally considered more aggressive than other adenocarcinomas because they are faster growing, more likely to spread to local lymph nodes and harder to completely remove at the time of surgery.
• Adenocarcinoid cancers (also known as Goblet Cell Carcinoids) are a hybrid tumor of both adenocarcinoma and a neuroendocrine (or carcinoid cancer) (see below). The expected behavior of adenocarcinoid tumors tends to follow that of the adenocarcinoma portion of the tumor. Consequently, treatment recommendations follow those for other types of appendiceal adenocarcinomas. They are generally considered to be more aggressive than low-grade or moderately-differentiated adenocarcinomas of the appendix, but not as aggressive as poorly-differentiated or signet ring cells adenocarcinomas.
• Neuroendocrine (Carcinoid) tumors. Neuroendocrine tumors arise from a subset of cells lining the appendix known as neuroendocrine cells. They do not make mucin and therefore do not cause PMP. They are generally considered to be slow growing and have a very different behavior than adenocarcinomas of the appendix.
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How common are Appendix Cancer and PMP?
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Estimates vary, but all tend to be within the category of “extremely rare.” PMP was once thought to be diagnosed in about 1,000 people world-wide each year. In other words, the lifetime odds of being diagnosed with PMP were thought to be about one in a million. However, specialists now believe it is more common than once thought, closer to one person diagnosed per 500,000 people per year.
Recent research indicates that the incidence of appendix cancer may be as high as 10 people diagnosed per million per year. The number of reported cases has increased over the past decade, but it is not certain whether incidence of appendix cancer is actually increasing or the rate has changed due to likely misdiagnosis or misclassification in the past.
PMP is listed among the rare or "orphan" diseases acknowledged by the National Association of Rare Disorders (NORD). An orphan disease is generally considered to have a prevalence of fewer than 200,000 affected individuals in the United States.
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Orphan diseases such as PMP have such a low prevalence in the general population that a doctor in a busy general practice is unlikely to see more than one case a year (if any). It also means that most pathologists see the disease infrequently and may misinterpret cell pathology, resulting in an incorrect diagnosis. Patients would benefit from improved awareness and diagnostic methods in the medical community through earlier detection and treatment of these diseases.
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Who typically is diagnosed with PMP?
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PMP affects men and women almost equally. The age at diagnosis ranges from late teens to late in life, with most individuals diagnosed in their 40's and 50's.
It is generally thought that there is no genetic (familial) link to PMP. Risk factors that might predispose an individual to develop PMP are unknown.
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What are the common symptoms of Appendix Cancer and PMP?
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Many patients lack clearly defined symptoms until the disease has reached a relatively advanced stage. The following are some of the commonly reported symptoms:
• Appendicitis
• Increased abdominal girth
• Bloating
• Pain/discomfort in the abdominal region—can be a dull ache or sharp pains similar to appendicitis
• Hernia symptoms—PMP is often initially diagnosed as a hernia, especially in men
• In women, symptoms of an ovarian cyst or tumor—PMP is often initially misdiagnosed as ovarian cancer
• Ascites (fluid) buildup in the abdominal cavity
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For more information about Appendix Cancer & PMP, please visit the ACPMP website.