The present study classified tumors of the appendix and reviewed treatments that aim to prevent cancer spread to the abdominal cavity.

Pseudomyxoma peritonei (PMP) is a rare condition caused by the production of too much mucin (a protein that is secreted in mucus).  PMP affects women more than men and symptoms may include pelvic pain, abdominal bloating, digestive disorders, weight change and infertility. If left untreated, the mucin build-up may compress vital tissues such as the liver, spleen and stomach.

Tumors generally involved in the development of PMP are usually low-grade appendiceal mucinous neoplasms (LAMN) more commonly known as tumors of the appendix. PMP does not spread through the lymphatic system or blood stream like other types of cancer. Instead it spreads (disseminates) through the abdominal cavity. How LAMNs are initially treated factors in the spread and development of PMP, and the use of risk-reducing cytoreductive surgery (debulking) is unclear.

This paper looks at 379 patients diagnosed with PMP between 2002 and 2009.  The authors identified that these patients had one of two types of LAMN.  These were either type 1, where the mucin produced was confined to the cavity of the appendix, either type 2, with the mucin invading the wall and/or outer wall of the appendix.  The 352 patients with a type 1 LAMN were treated with a watch and wait policy, with their tumour markers being regularly measured. Imaging studies were also performed in some of the patients. Patients with type 2 LAMN were treated with surgery to remove the affected area; part of the abdominal cavity's lining (peritoneum) or the gall bladder were removed without excision of the appendix. These patients were also treated with a warmed chemotherapy medication put directly into the abdominal cavity.

40 months after treatment no patients in either treatment group experienced disease progression. This shows that there are two types of LAMN.  Type 1 rarely invades the abdominal cavity or takes a long time to do so. Type 2 can be treated to reduce the chance of developing PMP.

As a result of this work, the authors’ current practice is to counsel women and excise gynaecological organs only if they look abnormal. Additionally, risk-reducing cytoreductive surgery is now offered where appropriate.

This study is limited due to its small number of participants. However, large trials are difficult to conduct because of the rare nature of the disease.