When people hear the word "mesothelioma," they often think of cancer caused by asbestos exposure that affects the lungs (pleura). But mesothelioma can also affect the peritoneum — the lining of the abdominal cavity — and this form is known as peritoneal mesothelioma. Among its subtypes, epithelioid peritoneal mesothelioma is the most common and generally the least aggressive.
Despite its relatively better prognosis, epithelioid peritoneal mesothelioma remains a rare and serious cancer that requires specialized care. In this blog post, we explore this disease in detail — its causes, symptoms, diagnosis, treatment options, and outlook.
📌 What is Peritoneal Mesothelioma?
Peritoneal mesothelioma is a malignant tumor that develops from the mesothelial cells lining the peritoneum, the thin membrane that encases the abdominal organs. It accounts for approximately 10–30% of all mesothelioma cases.
There are three main histological subtypes:
- Epithelioid (most common, ~75%)
- Sarcomatoid
- Biphasic (a mix of epithelioid and sarcomatoid)
The epithelioid subtype tends to respond better to treatment and is associated with a more favorable prognosis.
🧬 What Causes It?
The primary risk factor for all forms of mesothelioma, including peritoneal mesothelioma, is asbestos exposure. When asbestos fibers are inhaled or ingested, they can become embedded in tissues, leading to chronic inflammation and cellular mutations over decades.
Other potential contributing factors:
- Radiation exposure
- Genetic predisposition (e.g., BAP1 mutations)
- Simian Virus 40 (SV40) (controversial and not widely accepted)
- Zeolite exposure (in rare, specific geographies)
The latency period between asbestos exposure and disease development can be 20 to 50 years.
⚠️ Symptoms of Epithelioid Peritoneal Mesothelioma
Symptoms often develop slowly and are non-specific, which can delay diagnosis.
- Common signs and symptoms include:
- Abdominal pain or discomfort
- Abdominal swelling (due to ascites – fluid buildup)
- Unexplained weight loss
- Loss of appetite
- Nausea and fatigue
- Changes in bowel habits (diarrhea or constipation)
- Palpable abdominal masses (in advanced cases)
Because these symptoms are vague, many patients are initially misdiagnosed with conditions like irritable bowel syndrome, ovarian cancer, or gastrointestinal issues.
🧪 Diagnosis
Accurate diagnosis is complex and involves a combination of clinical, imaging, and pathological assessments.
1. Imaging Tests
CT Scan: Most useful for detecting peritoneal thickening, masses, and ascites.
MRI: Helpful for detailed soft tissue evaluation.
PET Scan: May identify active disease and metastasis.
2. Ascitic Fluid Cytology
Analysis of peritoneal fluid may show malignant cells.
However, cytology alone is often inconclusive.
3. Biopsy (gold standard)
Tissue biopsy via laparoscopy or image-guided needle biopsy is necessary.
Histopathology shows epithelioid cells arranged in tubular, papillary, or trabecular patterns.
4. Immunohistochemistry (IHC)
Essential for distinguishing mesothelioma from other cancers (especially metastatic adenocarcinoma):
Positive mesothelial markers:
- Calretinin
- WT-1
- D2-40 (podoplanin)
- CK5/6
Negative in mesothelioma (positive in adenocarcinoma):
- CEA
- MOC-31
- Ber-EP4
- B72.3
🧬 Molecular and Genetic Testing
Loss of BAP1 (BRCA1-associated protein 1) expression on IHC is frequently seen in epithelioid mesothelioma and can support the diagnosis.
Other genetic abnormalities may include CDKN2A and NF2 mutations.
These markers can help differentiate benign reactive mesothelial proliferations from malignant mesothelioma.
💊 Treatment Options
The treatment approach depends on:
- Disease stage
- Performance status of the patient
- Extent of peritoneal involvement
1. Cytoreductive Surgery (CRS) + HIPEC
This is the standard and most effective treatment for selected patients.
Cytoreductive surgery (CRS) removes all visible tumors.
Hyperthermic intraperitoneal chemotherapy (HIPEC) involves bathing the abdominal cavity with heated chemotherapy (usually cisplatin or mitomycin C) to kill remaining microscopic cancer cells.
🟢 Best candidates: Epithelioid histology, limited spread, good health status.
2. Systemic Chemotherapy
Used when surgery is not possible or as adjuvant treatment:
Pemetrexed + cisplatin or carboplatin is the most commonly used regimen.
3. Immunotherapy
Newer option with growing interest:
Checkpoint inhibitors like nivolumab and ipilimumab have shown promise, particularly for patients not eligible for surgery.
4. Targeted Therapy and Clinical Trials
Although not yet standard, targeted therapies and personalized medicine based on genetic profiles are under investigation in clinical trials.
🩺 Prognosis
Epithelioid peritoneal mesothelioma has a more favorable prognosis compared to other subtypes.
- Median survival with CRS + HIPEC: ~3–5 years or more
- Without treatment: Survival may be less than 1 year
- 5-year survival rate (with aggressive treatment): Up to 50%
Prognostic factors:
- Histological subtype (epithelioid > biphasic > sarcomatoid)
- Completeness of tumor removal (CRS)
- Patient’s age and general health
- Response to chemotherapy
🤝 Living with Peritoneal Mesothelioma
Being diagnosed with mesothelioma is life-altering. While the disease is serious, advancements in diagnosis and treatment have significantly improved outcomes for epithelioid cases.
Support groups, nutritional counseling, palliative care, and mental health support play crucial roles in helping patients maintain quality of life.
Feature
Origin
Risk Factor
Symptoms
Diagnosis
Treatment
Prognosis
Epithelioid peritoneal mesothelioma, though rare, is a potentially treatable disease when diagnosed early and managed at specialized centers. Awareness of its symptoms, risk factors, and treatment options is vital — not only for patients but also for healthcare providers who might encounter this condition.
If you or a loved one is facing this diagnosis, consult a multidisciplinary team experienced in mesothelioma care. With the right approach, there is hope and help available.
