Malignant Peritoneal Mesothelioma Mimicking Recurrent Diverticulitis.

Mesothelioma is an uncommon type of cancer arising from the mesothelial cells that form the lining of several cavities in the body. Exposure to asbestos is the leading known cause of mesothelioma. We present a 73-year-old male with a significant asbestos exposure and a recent history of recurrent diverticulitis who reported persistent left lower quadrant (LLQ) pain despite several courses of empiric antibiotic therapy. A recent computed tomography (CT) performed due to nonresolving symptoms showed possible nodularity of the mesentery and subsequent positron emission tomography (PET) scan demonstrated multiple hypermetabolic mesenteric lesions, notably in the left paracolic gutter. A colonoscopy was subsequently performed which demonstrated severe diverticulosis, but no obvious luminal lesions. The patient underwent an exploratory laparoscopy showing extensive peritoneal carcinomatosis involving all mesenteric surfaces and partial involvement of the right diaphragm. Final pathology revealed malignant epithelial mesothelioma with peritoneal seeding. The patient was referred to oncology and was started on hyperthermic intraperitoneal chemotherapy (HIPEC) and cytoreductive surgery (CRS). Our case highlights a challenging presentation of malignant peritoneal mesothelioma (MPM), which is often initially misdiagnosed due to vague symptoms. Physicians should consider further diagnostic workup for unrelenting LLQ abdominal pain after diverticulitis has been treated.