What Is Peritoneal Mesothelioma?

Understanding Peritoneal Mesothelioma

Peritoneal mesothelioma is a malignant cancer that forms in the peritoneum — the thin membrane that lines the abdominal cavity and covers the abdominal organs including the stomach, liver, intestines, and spleen. It is the second most common type of mesothelioma after pleural mesothelioma, accounting for approximately 20% of all mesothelioma diagnoses.

Like all forms of mesothelioma, peritoneal mesothelioma is caused by asbestos exposure. However, this type has a notably different treatment landscape. The development of cytoreductive surgery combined with HIPEC (heated intraperitoneal chemotherapy) has transformed outcomes for many peritoneal mesothelioma patients, offering significantly better survival rates than were possible even two decades ago.

How Asbestos Reaches the Abdomen

Researchers have identified two primary pathways by which asbestos fibers reach the peritoneum. The first is ingestion: when asbestos fibers are inhaled, they can become trapped in mucus in the airways and subsequently swallowed, traveling through the digestive system to the peritoneal lining. Workers who were exposed to heavy concentrations of airborne asbestos frequently ingested fibers this way.

The second pathway is translocation: inhaled fibers that reach the lungs may migrate through the lymphatic system or the diaphragm to the abdominal cavity. According to the National Cancer Institute, the precise mechanism is still under study, but both pathways are supported by clinical evidence.

Once in the peritoneum, asbestos fibers cause chronic inflammation and DNA damage to mesothelial cells. Over a latency period of 20 to 50 years, this damage can lead to the uncontrolled cell growth that characterizes mesothelioma.

Symptoms of Peritoneal Mesothelioma

The symptoms of peritoneal mesothelioma are primarily abdominal in nature and often develop gradually, which can make early diagnosis challenging. Many symptoms overlap with more common gastrointestinal conditions.

Abdominal pain and distension. A persistent ache or swelling in the abdomen is the most commonly reported symptom. As tumors grow on the peritoneal surface, they cause increasing discomfort and visible abdominal enlargement.

Ascites. The buildup of excess fluid in the abdominal cavity occurs in many peritoneal mesothelioma patients. Ascites contributes to the abdominal swelling and can cause a feeling of fullness or pressure.

Unexplained weight loss. Significant, unintentional weight loss is common as the disease progresses. This may result from decreased appetite, the metabolic demands of the cancer, or impaired nutrient absorption.

Bowel changes. Tumor growth on or near the intestines can cause changes in bowel habits, including constipation, diarrhea, or partial bowel obstruction. Nausea and vomiting may also occur.

Additional symptoms include fatigue, fever, and in some cases, a palpable mass in the abdomen. Because these symptoms overlap with many other conditions, informing your doctor about any history of asbestos exposure is critical for a timely diagnosis.

Diagnosis

Diagnosing peritoneal mesothelioma typically begins with imaging studies. CT scans of the abdomen can reveal peritoneal thickening, nodules on the peritoneal surface, and fluid accumulation. PET scans help determine the extent of disease spread.

A definitive diagnosis requires a tissue biopsy, most commonly obtained through laparoscopy — a minimally invasive procedure in which a surgeon inserts a small camera into the abdomen to visualize the peritoneum and collect tissue samples. Pathologists then use immunohistochemistry staining to confirm the mesothelioma diagnosis and identify the cell type (epithelioid, sarcomatoid, or biphasic).

Unlike pleural mesothelioma, there is no widely accepted formal staging system for peritoneal mesothelioma. Instead, doctors typically assess the Peritoneal Cancer Index (PCI), which scores the extent of tumor spread across 13 regions of the abdomen on a scale of 0 to 39. A lower PCI score generally correlates with better treatment outcomes.

HIPEC: The Breakthrough Treatment

The most significant advancement in peritoneal mesothelioma treatment has been the combination of cytoreductive surgery (CRS) with heated intraperitoneal chemotherapy, known as HIPEC. This two-part procedure has dramatically improved outcomes for eligible patients.

During cytoreductive surgery, a surgeon removes all visible tumors from the peritoneal surfaces. This may involve removing portions of the peritoneum, sections of affected organs, and any other tissue where cancer has spread. The goal is to eliminate as much visible disease as possible.

Immediately following surgery, heated chemotherapy solution — typically using cisplatin and other agents warmed to approximately 42 degrees Celsius (107.6°F) — is circulated directly throughout the abdominal cavity for 60 to 90 minutes. The heat enhances the penetration and effectiveness of the chemotherapy drugs, and the direct application allows much higher concentrations than would be possible with intravenous chemotherapy.

Research published in the Annals of Surgical Oncology has shown that patients who undergo complete CRS with HIPEC can achieve 5-year survival rates of approximately 50% or higher — a remarkable improvement compared to systemic chemotherapy alone, which historically offered median survival of approximately 12 months.

Prognosis and Survival

Peritoneal mesothelioma patients who are eligible for CRS with HIPEC generally have a more favorable prognosis than pleural mesothelioma patients treated with standard approaches. Several factors influence individual prognosis.

Patients with epithelioid cell type, a lower PCI score (indicating less extensive disease), complete cytoreduction (no remaining visible tumor), and younger age tend to have the best outcomes. For these patients, median survival following CRS with HIPEC can exceed 5 years at specialized centers.

Patients who are not candidates for surgery due to extensive disease, poor overall health, or sarcomatoid cell type may receive systemic chemotherapy (typically pemetrexed plus cisplatin), immunotherapy, or palliative care. Clinical trials continue to explore new treatment approaches for all peritoneal mesothelioma patients.