Unraveling Rare: Appendix Cancer (Pseudomyxoma Peritonei)

Pseudomyxoma peritonei (PMP) is a rare cancer that usually starts in the appendix. Most often a polyp starts in the appendix in the inner lining. It is very infrequently discovered at this stage because it is asymptomatic. As it gets larger, it grows through the wall of the appendix into the abdominal cavity where more tumors form. These tumors then secrete mucin, which is a jelly-like substance, which accumulates in the abdomen and causes symptoms when it becomes too much. Typically, this build up leads to abdominal swelling that causes the classic “jelly belly” and leads to compression of the abdominal organs.
It was first discovered in 1842 by Rokitansky and later named by Werth after he noted an association with ovarian mucinous tumors.
PMP seems to affect men and women equally, while some sources claim it is more common in females.  In appendiceal specimens examined, only 1% of them were found to have neoplasms. They account for only one half of one percent of intestinal neoplasms. Approximately 50% of these are carcinoid tumors. The majority of these occur in the distal one-third of the appendix where obstruction is unlikely to occur. The incidence of PMP is one per one million per year and found in 2 out of every 10,000 cases of gelatinous ascites. The median age at the time it is diagnosed is 54 years.
 
Signs and Symptoms 

• Increasing abdominal size (“jelly belly”)
• Abdominal pain
• Generally not painful to touch
• In men, can observe protrusion of parts of the intestines in the inguinal area
• In women, enlarged ovaries may be seen
• Without treatment, can lead to intestinal obstruction
• Loss of function of the intestines
• Poor food intake
• Malnutrition

No one knows what causes these tumors. There are no known familial or genetic factors. Most agree the appendix is the site of origin of PMP. It is believed that cells from the affected appendix leak into the abdominal cavity and implant on the peritoneum and other organs. They then replicate and produce a mucinous by-product that spreads throughout the abdomen.
There are several diagnostic tests used to confirm a diagnosis of PMP and appendiceal neoplasm in view of suggestive symptoms. CT scans are the most commonly used radiographic test used for this purpose. MRI scans and PET scans have likewise been used. Patients are typically monitored by scans following treatment. The conclusive diagnosis is made by the pathologist by directly examining a biopsy specimen. Some cases of PMP are found incidentally during surgery for other reasons.
Treatment of PMP depends of the histologic type but the mainstay of treatment remains surgery. Cytoreductive, or debulking surgery, is performed. Removal of any visible abdominal tumors is done as well as the appendix. The following may be removed as well: the omentum, spleen, gallbladder, ovaries, uterus, lining of the diaphragm, and intestines depending on what is observed during surgery. Immediately following the surgery, hyperthermic intraperitoneal chemotherapy (HIPEC) is administered directly into the abdomen to remove any remaining tumor cells. Additional, traditional chemotherapy may follow.
The pathologic subtype determines the ultimate survival. Other factors include extent of the disease and completeness of cytoreduction. In patients with less extensive disease, a 5-year survival rate of 82% is a reasonable goal. Patients with more incomplete cytoreduction had more disease and lower 5 year survival. In another study, the median survival was observed to be 9.8 years from the date of the initial surgery. Survival was significantly longer (12.8 years) in patients with low grade mucinous adenocarcinoma compared to those with high grade (4.0 years). While cytoreduction surgery proves to lengthen the life expectancy, patients often require further debulking surgeries.
Because of the rarity of this disease, not much research has been conducted and there no good clinical trials to date. More research is needed into this disorder and a clinical trial is needed to further exam debulking surgery in combination with HIPEC treatment to find the correct regimen to maximize life-expectancy.
 
About the Author
Dr. Linda Girgis MD, FAAFP is a family physician in South River, New Jersey. She has been in private practice since 2001. She holds board certification from the American Board of Family Medicine and is affiliated with St. Peter’s University Hospital and Raritan Bay Hospital. She teaches medical students and residents from Drexel University and other institutions.  Dr. Girgis earned her medical degree from St. George’s University School of Medicine. She completed her internship and residency at Sacred Heart Hospital, through Temple University where she was recognized as intern of the year.  She is a blogger for Physician’s Weekly and MedicalPractice Insider as well as a guest columnist for Medcity New, PM360 and HIT Outcomes. She has had articles published in several other media outlets. She has authored the books, “Inside Our Broken Healthcare System”, “The War on Doctors” and “The Healthcare Apocalypse.” She has been interviewed in US News and on NBC Nightly News.