SESSION TITLE: Fellows Lung Cancer Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: October 18-21, 2020 INTRODUCTION: Bronchus-associated lymphoid tissue (BALT) lymphoma is a rare marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). The incidence of MALT worldwide is estimated to be up to 1% of primary pulmonary lymphomas, most commonly endobronchial.(1) Infectious pathogens, amyloid deposition, rheumatological diseases and smoking have all been associated with pulmonary MALT to varying degrees.(2) Treatment is patient-specific, and ranges from observation to chemotherapy, radiation therapy or resection, usually with a favorable prognosis.(3) CASE PRESENTATION: We present a case of an asymptomatic United States Marine Corps F/A-18 fighter jet aviator who was incidentally found to have BALT, first identified as a 5mm lesion during a CT scan for an unrelated pericardial cyst four years earlier. The most recent imaging demonstrated the lesion to be similar in size to previous annual studies. To avoid further unnecessary exposure to radiation for a stable endobronchial lesion, we offered an inspection flexible bronchoscopy which confirmed the presence of a raised flesh-colored, polypoid lesion located in the medial right bronchus intermedius. PET/CT was non-avid. The lesion was easily biopsied and sent for pathological examination. After the diagnosis, the patient successfully underwent involved-site radiation therapy. He went on to receive a waiver from his flight surgeon to return to flight duty without limitations. DISCUSSION: Our case of BALT was diagnosed after it was noted incidentally on CT. Its radiographic appearance was consistent with other cases in the literature.(4, 5) This case underscores the importance of investigating such stable-appearing, non-resolving endobronchial lesions. In this instance, an efficient time course from diagnosis to treatment allowed this aviator to be cleared to fly again. CONCLUSIONS: Bronchus-associated lesions have a wide differential diagnosis.(5) This case highlighted how pursuit of such lesions may have clinical benefit, such as this case, which positively impacted this patient’s military flying career.(4) Reference #1: Takeshi K, Daisuke H, et. al. Endobronchial Mucosa-associated Lymphoid Tissue Lymphoma: A Report of Two Cases and a Review of the Literature. Intern Med. 2018; 57: 2233-2236. Reference #2: William J, Variakojis D, et. al. Lymphoproliferative Disorders. Archives of Pathology & Laboratory Medicine. 2013; 137: 382–391. Reference #3: Hiraishi Y, Iikura M, et. al. Two tracheal BALT lymphoma patients successfully treated with chemotherapy including rituximab. Respiratory Investigations. 2014; 52: 144- 146. DISCLOSURES: No relevant relationships by Neil Partain, source=Web Response