Introduction: Malignant Mesothelioma is an exceptionally rare and aggressive neoplasm originating from the mesothelial cells lining the peritoneum, exhibiting an inclination to extensively spread within the abdominal cavity. The predominant morbidity and mortality associated with this malignancy arise from the progression of the disease within the peritoneum, with metastatic spread beyond the abdominal cavity being uncommon. Approximately 3300 cases of mesothelioma are diagnosed annually in the United States, with only 10-15 percent manifesting as the peritoneal variant. Pleural involvement is more prevalent, positioning the peritoneum as the second most frequent site of origin.

While asbestos exposure is a well-established link to mesothelioma, the association with Malignant Peritoneal Mesothelioma (MPM) is not as robust as it is for its pleural counterpart. The underrepresentation of MPM in molecular and clinical studies is attributed to its lower incidence compared to pleural mesothelioma, rendering it an understudied disease. Despite the commonality in asbestos exposure between pleural and peritoneal mesothelioma, disparities in their gene expression profiles suggest distinct molecular pathogenesis.

Case Presentation: A 75-year-old male, with a medical history encompassing glaucoma, COPD, benign prostatic hyperplasia (BPH), and recently diagnosed mesothelioma, presented to the emergency department. He reported a two-week progression of abdominal distension, early satiety, and dyspnea aggravated by activity. One year prior, he initiated a medical evaluation for fluid retention and abdominal distension. A recent omental biopsy, conducted a month before presentation, confirmed the diagnosis of mesothelioma, prompting the initiation of chemotherapy every three weeks. Despite paracentesis performed monthly, the patient experienced worsening shortness of breath and early satiety post-chemotherapy. Generalized weakness, a four-day lapse in bowel movements attributed to reduced food intake, and the absence of fever, chills, palpitation, cough, chest pain, headache, nausea, or vomiting were reported.

Clinical Features: Malignant Peritoneal Mesothelioma poses a diagnostic challenge due to the absence of specific signs or symptoms. Common manifestations include abdominal distension, pain, early satiety, weight loss, dyspnea, chest pain, and fatigue. Rare symptoms encompass new-onset hernia, fever of unknown origin, night sweats, or incidental findings during physical examinations or laparoscopy. Delays in presentation and diagnosis contribute to the advanced stage of diagnosis, with most cases having already spread throughout the abdominal cavity.

Three distinct presentations of MPM include the Dry Painful Type, characterized by abdominal pain with minimal ascites; the Wet Type, presenting with abdominal distension and ascites; and the Mixed Type, combining abdominal pain and distension. Paraneoplastic phenomena, such as fever, thrombocytosis, malignancy-related thrombosis, hypoglycemia, hypoalbuminemia, paraneoplastic hepatopathy, and rarely, Coombs-positive Hemolytic anemia, further complicate the clinical picture.

Investigations: Surgical gross and microscopic descriptions of liver biopsies indicated chronic hepatitis with mild portal inflammation, grade 1, and no fibrosis, stage 0. Notably, the omental biopsy performed on confirmed Malignant Mesothelioma of the epithelioid type. Immunohistochemical stains supported the diagnosis, revealing positivity for CK AE1/AE3, calretinin, WT1, CK7 (focally), and GATA3 (focally), while testing negative for BAP1, CDX2, chromogranin, CK20, hepatocyte antigen, PAX8, PSA, synaptophysin, and TTF1.

Treatment: Due to the rarity of MPM, no standardized treatment protocols exist. Cytoreductive surgery (CRS) and hyperthermic intraoperative peritoneal perfusion with chemotherapy (HIPEC) are recommended for selected patients without extraperitoneal disease spread, possessing a good performance status and potential for complete surgical cytoreduction. Systemic chemotherapy, particularly pemetrexed-based regimens, is advocated for patients ineligible for CRS/HIPEC.

Discussion: The absence of randomized controlled trials for MPM treatment underscores the challenges in guiding therapeutic decisions. While systemic chemotherapy with pemetrexed has shown promise, the lack of comprehensive studies specific to MPM necessitates a nuanced approach to treatment planning. Immunotherapy’s role in MPM management remains an evolving area, with ongoing research aiming to elucidate its potential benefits.

Conclusion: Malignant Peritoneal Mesothelioma, characterized by aggressive intra-abdominal spread, poses significant diagnostic and therapeutic challenges. The scarcity of standardized treatment guidelines accentuates the importance of ongoing research to enhance our understanding of this rare neoplasm, paving the way for improved diagnostic modalities and targeted therapeutic interventions.

References and Resources

1. Kim J, Bhagwandin S, Labow DM. Malignant peritoneal mesothelioma: a review. Ann Transl Med. 2017 Jun;5(11):236.
2. UpToDate. Malignant peritoneal mesothelioma: Epidemiology, risk factors, clinical presentation, diagnosis, and staging.
3. Sharma H, Bell I, Schofield J, Bird G. Primary peritoneal mesothelioma: Case series and literature review. Clin Res Hepatol Gastroenterol. Jan 2011;35:55–59.