Mucinous Adenocarcinoma of the Appendix
and Pseudomyxoma Peritonei (PMP)

Tumors that produce mucous (mucinous tumors) of the appendix are rare. Normally a thin layer of cells lining the inside of the appendix produce mucous in small amounts. These cells normally die off at the same rate they reproduce. In cases of tumors, the cells reproduce faster than they die off and create a mass of cells. These masses of cells, or tumors, can produce large amounts of mucous.

There are different types of mucous-producing tumors that can occur in the appendix. There are both benign and cancerous mucous-producing tumors. Mucinous Adenocarcinoma is a cancerous tumor of the appendix; it is the most common type of appendix cancer. Mucinous Adenoma (also called Mucinous Cystadenoma) is a benign, or low-grade tumor of the appendix.

Benign tumors differ from cancerous tumors in that benign tumors don't usually invade normal tissue or spread (metastasize) to other areas of the body, while cancerous tumors often do both. Both mucinous adenocarcinoma and mucinous adenoma tumors can release cells into the abdomen. The released cells travel in the fluid that normally circulates in the abdomen and adhere to the inner surfaces (peritoneal surfaces) of the abdomen. Some tumor cells may also settle in parts of the abdomen and pelvis. These mucous-producing cells that are freed into the abdomen grow into new tumors that create mucous.

Benign mucous-producing appendix tumors may still cause death if they grow rapidly or create too much mucous, and because of this benign tumors are referred to as low-grade malignancies when they spread into the abdomen. Very large amounts of thick mucous can be produced by both the benign and cancerous types of tumors and can cause the abdomen to become bloated with mucinous ascites. A slang term for the large amounts of this thick mucous in the abdomen is "jelly belly". Organs in the abdomen can become "squashed" by this mucous, and death can eventually result. In this circumstance the benign cells cause damage in much the same way as cancerous tumors that produce mucous, so are considered in the medical community to be a low-grade cancer. With treatment, however, survival outcomes from the benign, or low-grade mucous-producing tumors (mucinous adenoma) are much better than outcomes for high-grade cancerous mucous-producing tumors (mucinous adenocarcinoma). See below more information about the different types of mucous-producing tumors of the appendix.

Mucinous Adenocarcinoma (Mucinous Cystadenocarcinoma)

Mucinous adenocarcinoma is the most common cancer of the appendix. It accounts for about 37% of all appendix cancers. This high-grade cancerous tumor produces mucous, but also more commonly invades soft tissues and organs. This tumor may also grow faster and is more likely to metastasize (spread) to the lymph nodes, liver and lung than mucinous adenoma. The medical term for extensive spread of these cancerous mucous-producing tumors into the abdomen is Peritoneal Mucinous Carcinomatosis (PMCA).

Mucinous Adenoma (Mucinous Cystadenoma)

Mucinous adenoma is a slow-growing benign or precancerous cyst-like tumor of the appendix, in which tumor cells produce mucous. If the adenoma ruptures, the mucous producing adenoma cells are released into the abdomen along with the mucous. These cells form mucous producing tumors. Extensive spread of these benign mucous producing tumors into the abdomen is referred to medically as DPAM (Disseminated Peritoneal Adenomucinosis), or just "adenomucinosis". Though this tumor is considered benign, it is classified as a low-grade malignancy as it can still be fatal if untreated. Because this tumor is less invasive, it is more likely that complete cytoreduction will be achieved with surgical intervention.

Pseudomyxoma Peritonei (PMP)

Pseudomyxoma Peritonei (PMP) is a more common name given to the "jelly belly" syndrome caused by mucinous adenoma and mucinous adenocarcinoma. The term Pseudomyxoma Peritonei means "false mucinous tumor of the peritoneum". Pseudomyxoma Peritonei (PMP) is commonly used to refer to widespread mucinous disease in the abdomen caused by either mucinous adenoma or mucinous adenocarcinoma. Most currently, though, the label Pseudomyxoma Peritonei (PMP) is starting to be used for DPAM (Disseminated Peritoneal Adenomucinosis), or "jelly belly" that is caused by tumors that are benign or pre-cancerous. Separating the two tumor types when defining PMP is helpful for research purposes as outcomes with the same treatment are much different for the two types of tumors.

Both Pseudomyxoma Peritonei (PMP) and Peritoneal Mucinous Carcinomatosis (PMCA) commonly recur after treatment.

Another great resource for information about this disease can also be found at the site:

PMP Awareness Organization


  • Appendicitis may be the first symptom of both Mucinous Adenocarcinoma and Mucinous Adenoma of the appendix. Both Mucinous Adenocarcinoma and Mucinous Adenoma tumors may cause the abdomen to increase in size, or form masses in the abdomen or in the pelvis. In men the first symptom is sometimes an inguinal hernia, in women it often presents as an ovarian mass.


  • Treatment for a benign mucinous adenoma that has not ruptured and that is confined to the appendix is removal of the appendix. If there is any possibility of the cyst being ruptured during laparoscopic removal, the abdomen should be opened surgically to avoid rupture of the cyst into the abdomen. If the cyst does rupture into the abdomen, the cells released may later become tumors and produce large amounts of mucous (adenomucinosis), causing the syndrome Pseudomyxoma Peritonei (PMP). If the appendix is removed laparoscopically, the appendix should be contained in a plastic bag to avoid spilling mucous and cells into the abdomen.

  • Treatment for mucinous adenocarcinoma confined to the appendix when the appendix has not ruptured is appendectomy and right hemicolectomy (surgical removal of the appendix and up to half of the right side of the colon).

  • Treatment for of mucinous tumors that have spread extensively into the abdomen, either benign or cancerous- Pseudomyxoma Peritonei (PMP) or Peritoneal Mucinous Carcinomatosis (PMCA) is the same: cytoreduction (debulking) surgery to remove mucous and tumor implants in the abdominal cavity followed by intraoperative hyperthermic peritoneal chemotherapy. Early postoperative intraperitoneal chemotherapy (EPIC, in which chemotherapy liquid is put into the abdomen using a port or tube soon after the surgery is over), may also be used.

  • IV chemotherapy (chemotherapy given into a vein) may possibly be used in addition for treatment of Mucinous Adenocarcinoma, but is not usually used for treatment of Mucinous Adenoma.

Risk Factors:

  • Most common 6th decade of life, mean age of occurrence 60 years old. Disagreement in the literature as to male-female ratios.


  • Removal of the appendix for Mucinous Cystadenoma that has not spread beyond the appendix is considered curative.

  • Prognosis for both Mucinous Adenoma and Mucinous Adenocarcinoma depends on the grade of malignancy of the mucinous tumor and the success of debulking surgeries in removing all tumors that have metastasized into the abdomen.

  • For low-grade Mucinous Adenoma that has spread beyond the appendix into the abdomen, and for Pseudomyxoma Peritonei (PMP), 5 year survival has been reported in some studies to be over 75-80% when treated with cytoreduction (debulking) surgery to remove all of the tumors in the abdomen combined with hyperthermic intraoperative peritoneal chemotherapy (HIPEC).

  • For high-grade Mucinous Adenocarcinoma that has spread beyond the appendix into the abdomen, and for Peritoneal Mucinous Carcinomatosis (PMCA), 5 year survival has been stated in some studies to be approximately 50% when treated with cytoreduction (debulking) surgery to remove all of the tumors in the abdomen combined with hyperthermic intraoperative peritoneal chemotherapy (HIPEC).

Last Update:2013-01-12 23:16:53