UNUSUAL CASE OF DIFFUSE CYSTIC LUNG DISEASE

Abstract

SESSION TITLE: Monday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Cystic lung disease is a group of heterogeneous pulmonary diseases resulting from hereditary/congenital, systemic disorders and infectious causes among others. Malignancy is not a usual cause of cystic lung disease. We present a case of pulmonary mucinous cystadenocarcinoma (PMC) that presented as cystic lung disease. CASE PRESENTATION: Sixty six year old male former smoker was admitted in May 2018 with cough and dyspnea. Examination revealed rhonchi bilaterally. Chest radiograph revealed bilateral diffuse patchy alveolar infiltrates prompting Chest CT scan that revealed alveolar consolidations and numerous cavitary lesions with mediastinal and hilar lymphadenopathy. Bronchoscopy with lavage yielded Streptococcus pneumoniae with negative cytology for malignancy. He was treated with antibiotics with minimal improvement. He was subsequently seen at pulmonary office and had extensive collagen vascular serology tests, which were negative. He underwent repeat bronchoscopy including EBUS-TBNA of paratracheal lymph nodes, which was non-diagnostic. Having reported 40-pound weight loss he underwent robotic right upper lobe biopsy that revealed well-differentiated mucinous adenocarcinoma, which was EGFR/ALK negative. He later had biopsy of left lower lobe after extensive discussion at tumor board, which showed the same pathology. PET CT showed multiple bilateral cavitary lesions with no hypermetabolic activity. He was treated with carboplatin-based chemotherapy. Repeat chest CT after two treatments showed marked progression of innumerable cavitary metastatic lesions throughout both lungs, with tumors coalescing, and new extensive ground glass infiltrates. Oncology is presently considering 2nd line chemotherapy. DISCUSSION: PMC is a very rare type of lung cancer in the colloid adenocarcinoma spectrum that was initially described by Gowar in 1978. It commonly involves bilateral lower lobes and is commonly uni- or oligolocular unlike our case although multicystic PMC is not unusual. The incidence of PMC’s is unknown probably due to it’s rare nature with a 2011 publication reporting that only 20 cases were documented then. Diagnosing PMC can be an extremely challenging since bronchoscopy with BAL/washing/Transbronchial biopsy and FNA are often inconclusive probably due to malignant cells usually floating in the mucin. Furthermore mucinous adenocarcinoma tumor cells and submucosal mucinous glands of bronchial tissue can mimic each other morphologically. Therefore diagnosis is usually made by surgical biopsy. FDG PET activity may vary but tend to be low. Biological behavior of PMC is unknown with limited data suggesting low malignancy potential unlike our case. Treatment and natural history of PMC is unclear. CONCLUSIONS: This case illustrates the importance of maintaining a broad differential diagnosis. Reference #1: Gowar FJS. An unusual mucous cyst of the lung. Thorax. 1978;33:796–799. https://doi.org/10.1136/thx.33.6.796. DISCLOSURES: No relevant relationships by Pius Ochieng, source=Web Response No relevant relationships by Ajay Shetty, source=Web Response No relevant relationships by Pandi Todhe, source=Web Response