Abstract: Malignant peritoneal mesothelioma (MPeM) is a rare cancer of the peritoneum with a poor prognosis and nonspecific clinical course. We discuss a case of MPeM in a 59-year-old male who presented with abdominal pain and distension, without any known previous asbestos exposure. The diagnosis was made after a second biopsy finally confirmed epithelioid MPeM in an advanced stage with pleural effusion. The patient underwent six cycles of chemotherapy with cisplatin and pemetrexed, experienced disease progression, and was then started on pembrolizumab as a second-line treatment. The patient achieved a complete response after two years of treatment with pembrolizumab and has been disease-free for almost four years with an Eastern Cooperative Oncology Group (ECOG) performance status of 0. Despite the lack of evidence to support the treatment with immunotherapy for MPeM, our case report encourages its use, highlighting its ability to enable a complete response with pembrolizumab with an excellent quality of life.
Introduction: Mesothelioma is a malignancy of the mesothelium, the serosal membrane that covers and protects the internal organs of the body. Malignant mesotheliomas predominantly affect the pleural mesothelium (50-60%) and can affect the peritoneum in 20-30% of cases [1]. The global incidence of malignant peritoneal mesothelioma (MPeM) is approximately one per four to five million population, while that of all mesotheliomas is one per one million people. Although the association between asbestos exposure and peritoneal mesothelioma is less strong than in the case of pleural mesothelioma, there is a history of asbestos exposure in approximately 50% of the cases [1].
Malignant mesothelioma has three subtypes with different degrees of aggressiveness: epithelioid (75-90% of cases), sarcomatoid, and biphasic. Epithelioid mesothelioma has the best overall prognosis among the malignant subtypes [2]. The clinical presentation of [ malignant peritoneal mesothelioma (MPeM) ] is often nonspecific, and a definite diagnosis can only be established by histological examination with immunocytochemical procedures, obtained by laparoscopy or open surgery. Pathologically, positive immunostaining for calretinin enhances the accuracy of the diagnosis [2,3].
Case Presentation: A 59-year-old male presented with abdominal pain and distension associated with a 7% weight loss over two months in September 2018. No history of fever, obstipation, diarrhea, nausea, or vomiting was documented. The patient was a truck driver, with a past medical history of hypertension treated with amlodipine (5 mg), type 2 diabetes treated with metformin (1000 mg), hypercholesterolemia treated with simvastatin (20mg), and Pott’s disease at the age of 17 years old managed with the transplantation of a portion of the right tibia into the spine. He had never smoked and had no known previous exposure to asbestos. There was no family history of cancer. Clinical examination revealed moderate ascites, without signs of chronic liver disease. The cardiovascular and respiratory examination was normal. Blood analysis, including full blood count, kidney and liver function tests, inflammatory markers, hepatitis, a viral and autoimmune screens, were all normal (including carcinoembryonic antigen, CA 19.9, and prostate specific antigen).
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