Pseudomyxoma peritonei (PMP) is a rare and complex condition characterized by the progressive accumulation of a jelly-like substance, known as mucin, within the abdominal cavity. This slow-growing malignancy, sometimes colloquially referred to as “jelly belly,” primarily affects the peritoneum, the membrane lining the abdominal wall and covering the organs. PMP is generally considered a low-grade malignant condition due to its localized growth pattern, but its rarity and unique spread often contribute to delayed diagnosis and necessitate specialized treatment. It can be life-threatening if left untreated.
Understanding the Nature of Pseudomyxoma Peritonei
The pathology of PMP is defined by the extensive production and spread of mucin secreted by the tumor cells. This disease almost always originates from a mucinous tumor in the appendix, though less common primary sites include the colon or, rarely, the ovary. When the primary tumor ruptures or penetrates the organ wall, it releases mucin-producing epithelial cells into the abdominal space.
These free-floating cells do not typically spread through the bloodstream or lymphatic system like most other cancers, accounting for the disease’s localized nature. Instead, the cells and the mucin they secrete are passively redistributed throughout the peritoneal cavity by the natural flow of peritoneal fluid. This “redistribution phenomenon” causes the tumor cells and mucin to accumulate at specific sites, such as the greater omentum, the pelvis, and beneath the diaphragm.
The continuous accumulation of mucin creates the characteristic “jelly belly” effect, enveloping and compressing internal organs. PMP is histologically classified into distinct categories: low-grade and high-grade. Low-grade PMP, often called disseminated peritoneal adenomucinosis (DPAM), is characterized by bland cells and a better prognosis. High-grade PMP, or peritoneal mucinous carcinomatosis (PMCA), involves more aggressive cellular features.
Identifying Symptoms and Initial Presentation
Because PMP is slow-growing, it often remains asymptomatic for many years, making early detection challenging. When symptoms appear, they are usually non-specific and related to the pressure exerted by the growing volume of mucin on abdominal organs. The most common symptom is a gradual increase in abdominal girth or unexplained weight gain, caused by the accumulating mucinous ascites.
Patients may also experience chronic abdominal or pelvic pain, feelings of fullness, or discomfort. As the disease progresses, it can affect bowel function, leading to changes in bowel habits, such as constipation, or the development of a hernia. In women, the disease can sometimes present as an ovarian mass, leading to a frequent initial misdiagnosis as ovarian cancer or ovarian cysts.
Confirmatory Diagnosis Methods
Confirming a PMP diagnosis relies on advanced imaging, blood tests, and pathological confirmation. Cross-sectional imaging, such as a Computed Tomography (CT) scan, is a primary tool used to visualize the extent of the mucin within the abdomen. A characteristic finding on a CT scan is the “scalloping” effect, where dense mucin collections compress and indent the surfaces of the liver and spleen.
Magnetic Resonance Imaging (MRI) is utilized for its superior soft-tissue resolution, which helps delineate the distribution of the mucin. Blood tests include tumor markers, particularly Carcinoembryonic Antigen (CEA) and Cancer Antigen 125 (CA-125), which may be elevated. While not conclusive alone, an elevated CA-125 level combined with specific CT findings can be highly suggestive of a high-grade tumor.
Definitive diagnosis requires a biopsy or cytological analysis of the mucin and epithelial cells, usually obtained during an exploratory procedure. Given the rarity and complex classification of PMP, tissue samples should be reviewed by a specialized pathologist. The final pathological grading is essential, as the distinction between low-grade and high-grade PMP significantly influences the treatment plan and prognosis.
Comprehensive Treatment Strategies
The standard of care for PMP is a two-part strategy performed at specialized centers. The first is Cytoreductive Surgery (CRS), which involves the surgical removal of all visible tumor deposits and mucin from the abdominal cavity. This procedure requires meticulous effort to strip the peritoneum and remove affected organs, such as the spleen, gallbladder, and portions of the bowel, to achieve the most complete clearance possible.
Following the surgical removal of the macroscopic disease, the abdominal cavity is immediately treated with Hyperthermic Intraperitoneal Chemotherapy (HIPEC). This technique involves circulating a heated chemotherapy solution, typically containing agents like Mitomycin C or Oxaliplatin, directly into the abdomen for approximately 90 minutes. The solution is warmed to a temperature of about 41 to 43 degrees Celsius.
The heat enhances the penetration of the chemotherapy drugs into the tissues and is cytotoxic to cancer cells. The direct application ensures a high concentration of the drug reaches the microscopic residual disease left behind after CRS, minimizing systemic side effects typically associated with intravenous chemotherapy. Successful long-term outcomes are directly linked to the completeness of the cytoreduction, emphasizing the necessity of a highly experienced multidisciplinary team.
Palliative Care
For patients with advanced or widespread disease where curative CRS/HIPEC is not feasible, palliative options focus on symptom management. This may involve less aggressive surgical debulking, such as an omentectomy, to relieve pressure and pain, or the use of systemic chemotherapy regimens like low-dose oral capecitabine to stabilize the disease and improve quality of life.
Long-Term Monitoring and Prognosis
The long-term outlook for PMP patients depends on the pathological grade of the tumor and the completeness of the cytoreductive surgery. Following successful CRS and HIPEC, patients with low-grade PMP have a better prognosis, with reported 5-year survival rates ranging from 64% to over 80%. In contrast, patients with high-grade PMP face a more challenging course, with 5-year survival rates dropping to approximately 30% to 50%.
Due to the risk of recurrence, which can be as high as 44% in some series, long-term surveillance is mandatory for all treated patients. This monitoring typically involves regular follow-up visits, blood work to check tumor marker levels, and periodic imaging, such as CT or MRI scans. Surveillance detects any signs of mucin reaccumulation or tumor regrowth early, allowing for potential re-treatment.