SESSION TITLE: Lung Cancer SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: Invasive mucinous adenocarcinoma (IMA) of the lung accounts for 5% of lung adenocarcinomas. It commonly presents as a mass or lobar consolidation. We describe a rare presentation of advanced IMA. CASE PRESENTATION: A 36-year-old healthy woman presented with dyspnea for 3 weeks. Admission vitals were Temp 97.9 F, BP 103/79, HR 77, RR 18, SpO2 97% on 2L nasal cannula. Exam was notable for a cachectic, non-toxic appearing woman with diffuse expiratory wheezing and decreased breath sounds at the right lung base. Laboratory studies were unremarkable (Table 1). CXR and CT showed extensive multi-lobar consolidations (Fig 1a,b). She disclosed having eight parakeets and two turtles at home. The working diagnosis was hypersensitivity pneumonitis from bird exposure. Bronchoscopy with trans-bronchial biopsies showed alveolar pneumocyte hyperplasia without atypia. She was prescribed prednisone 1mg/kg PO daily. She returned multiple times with persistent symptoms and worsening radiographic findings (Fig 2). She required bilevel ventilation with 100% FiO2 and was deemed too unstable for open lung biopsy. A transthoracic CT guided core needle lung biopsy was done; pathological findings were identical to the trans-bronchial biopsy (Fig 3). Samples were sent for a second opinion to a local expert; IMA was diagnosed. Her hypoxemia worsened requiring intubation. Despite mechanical ventilatory support, she had refractory hypoxemia and was started on V-V ECMO with the goal of receiving palliative chemotherapy. She received one cycle of platinum-based chemotherapy and subsequently developed multi-organ system failure; ECMO was stopped and she was palliatively extubated. DISCUSSION: Multi-lobar consolidations are typically seen in the setting of pneumonia; however, they are present in other disease processes. The case patient had an indolent presentation, was non-toxic appearing, and lacked fever and leukocytosis, making an infectious pneumonia unlikely. In the case patient, imaging revealed extensive multi-lobar consolidations which progressed over weeks. Little is known about IMA progression; treatment outcomes are guided by small retrospective studies. Platinum based chemotherapy is used as first line treatment, however, it has not been shown to significantly improve survival in stage IV disease. In stage I disease, resection and adjuvant chemotherapy has improved 5-year survival with rates of 93%. CONCLUSIONS: Clinicians should build a broad differential for multi-lobar consolidations especially when patient's presentation is inconsistent with a pulmonary infection. Tissue is crucial to arriving at the correct diagnosis. In this case, the initial presentation was consistent with hypersensitivity pneumonitis. However, the patient's lack of improvement with therapy prompted the search for an alternative diagnosis. Further investigation is needed to elucidate IMA disease prognostication and treatment regimens. Reference #1: Cha, YJ, and Hyo Sup Shim. Biology of Invasive Mucinous Adenocarcinoma of the Lung. Translational Lung Cancer Research 6.5 (2017): 508-512. Reference #2: Lee, HY, Cha, MJ, Lee, KS et al Prognosis in Resected Invasive Mucinous Adenocarcinomas of the Lung: Related Factors and Comparison with Resected Non-mucinous Adenocarcinomas Journal of Thoracic Oncology 6 (2017): 1064-1073. Reference #3: Koo H, Kim M, Kim H, et al. Computerized margin and texture analyses for differentiating bacterial pneumonia and invasive mucinous adenocarcinoma presenting as consolidation. Plos ONE 2017;12(5):1-14 DISCLOSURES: No relevant relationships by Bisma Alam, source=Web Response No relevant relationships by Yonatan Greenstein, source=Web Response