A80-3-10 Pleural Mesothelioma as Manifestation of Peritoneal Mesothelioma With Metastasis in a Young Patient

Introduction Malignant mesothelioma is most commonly associated with pleural malignancies, and prior asbestos exposure is a common risk factor in > 80% of all pleural mesothelioma cases (1). Abdominal peritoneal malignant mesothelioma, on the other hand, is a rare manifestation of mesothelioma with just a 15-20% incidence in all mesothelioma cases, and it is often incidentally discovered on imaging obtained for other reasons. It has a very indolent course with discovery usually very late in the disease process, which leads to a nearly 100% fatality rate at one year in nearly all cases (2, 3). The following case illustrates a rare presentation of malignant mesothelioma of the abdominal cavity which was discovered after a thoracentesis and chest tube placement for management of a pleural effusion. Case A forty-two-year-old female lifetime nonsmoker with no significant past medical history presented to the hospital for a large pleural effusion noted on chest x-ray imaging that was obtained at a local urgent care facility after two months of upper respiratory symptoms, dyspnea and fatigue. Upon arrival to the hospital, she underwent Interventional Radiology-guided thoracentesis with 1.5L of fluid removal; however, the fluid quickly re-accumulated within one day and Pulmonary consultation was requested for chest tube placement. Laboratory studies were consistent with an exudative, neutrophilic predominant effusion via protein and lactate dehydrogenase (LDH) criteria. Cytologic exam unexpectedly showed cells consistent with mesothelioma, despite no history of asbestos exposure or prior chest imaging suggestive of mesothelioma disease. She was promptly referred to Oncology, where further imaging and exploratory surgery revealed she had malignant mesothelioma of the peritoneum with a pelvic mass and dense abdominal disease with pulmonary metastasis. She received induction chemotherapy with Carboplatin/Pemetrexed/Pembrolizumab and subsequently received Pressurized Intraperitoneal Aerosolized Chemotherapy (PIPAC) for treatment of her disease at a specialized center. She continues on maintenance chemotherapy. Discussion This case illustrates a rare presentation of malignant pelvic mesothelioma diagnosed by thoracentesis in an otherwise healthy young patient without prior asbestos exposure. She was later discovered to have a primary tumor in the abdominal cavity, and her pleural manifestations on presentation were actually a sign of distant metastasis of a primary peritoneal mesothelioma, a universally fatal diagnosis. This rare presentation highlights the possibility of pleural mesothelioma being a manifestation of abdominal disease, and providers should maintain an index of suspicion for distant disease when diagnosing mesotheliomas of the lung. This abstract is funded by: None