SESSION TITLE: Medical Student/Resident Lung Cancer Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Malignant pleural mesothelioma (MPM) is the primary malignant tumor of the pleura which is highly aggressive with median survival around 12 months. This cancer is linked with asbestos exposure, but in 20% cases, the exposure fails to be found. CASE PRESENTATION: A 73 year- old lifetime non-smoking female presented with sharp, non-radiating, lower right chest pain. Her vital signs were normal and the physical exam was significant only for mild tenderness over her right flank. A CT angiogram of chest showed a soft tissue mass within the right posterior pleura measuring up to 3.4cm with enlarged subcarinal lymph nodes measuring up to 15mm. She denied any direct or indirect asbestos exposure, worked as a homemaker and her husband worked in agriculture. Subsequent PET scan was compatible with a malignant process. Bronchoscopy with biopsy of the subcarinal lymph node showed a poorly differentiated epithelioid neoplasm. A confirmatory CT-guided biopsy showed the same. Tumor cells had a high nuclear-cytoplasmic ratio, hyperchromatic nuclei with irregular contours. The cells showed positive immunostaining with Calretinin, WT-1, GATA-3, D2-40. The above workup was consistent with an atypical presentation of mesothelioma, stage IIIA (cT3N1), not felt to be resectable given subcarinal nodal involvement, and the patient underwent radiation followed by systemic chemotherapy. DISCUSSION: MPM affects men in 80% of cases and it is most frequent around the age of 60 years [1]. The male to female ratio is 4:1 with a predominance of right side over the left. The main etiological factor is previous exposure to asbestos with a typical long latency period of around 20 - 40 years. Few cases of MPM without asbestos exposure have been reported in literature [2,3]. The possibility of association of MPM and exposure to some dust or chemicals (stone cutter, leather factory or textile factory worker, agricultural chemicals) has also been reported. Typical presentation includes progressive dyspnea, cough and chest pain . Weight loss and generalized fatigue are seen at advanced stages and linked with poor outcomes. The most common radiological presentation is a unilateral pleural effusion, which is recurrent, and sometimes exudative and hemorrhagic. Bronchoscopy has a high sensitivity of 95% for diagnosis of MPM. In our case the patient is a lifetime non-smoker without any direct or indirect asbestos exposure. CONCLUSIONS: MPM has a poor prognosis despite advancement in surgery and oncology. Although linked with asbestos exposure, in 20% of the cases this exposure fails to be found. A significant increase in survival among MPM patients can be reached through earlier diagnosis. This case was unusual in that the initial presentation was due to pain, there was no significant pleural effusion identified, and no known exposure to asbestos. Reference #1: Robinson BW, Musk AW, Lake RA. Malignant mesothelioma. Lancet. 2005; 366:397-408. Reference #2: Batahar SA, Ouradi O, Elidrissi S, Amro L. Pleural Mesothelioma with No Asbestos Exposure: A Case Report. Journal of Clinical and Diagnostic Research : JCDR. 2016 Nov;10(11):OD07-OD08. DOI: 10.7860/JCDR/2016/21066.8849. Reference #3: Kant S, Verma SK, Sanjay. Malignant pleural mesothelioma without asbestos exposure with distant metastasis in a peripheral lymph node: a case report. Lung India. 2008;25(1):31–33. doi:10.4103/0970-2113.44137 DISCLOSURES: No relevant relationships by SYED ABBAS, source=Web Response No relevant relationships by Amarpreet Bhalla, source=Web Response No relevant relationships by Aditi Desai, source=Web Response No relevant relationships by Vivek Murthy, source=Web Response