TYPE: Case Report TOPIC: Signs and Symptoms of Chest Diseases INTRODUCTION: MALT (mucosa-associated lymphoid tissue) lymphoma is type of marginal zone non-Hodgkin lymphoma of B-cell origin that can rarely involve the lungs. We hereby present a case of pulmonary MALT lymphoma in a patient with Sjögren’s syndrome that presented with extensive cystic lung changes that was initially confused with lymphangioleiomyomatosis (LAM). CASE PRESENTATION: A 44-year-old former smoker female presented with worsening dyspnea on exertion and dry eyes and mouth. Chest CT had previously demonstrated numerous thin-walled cysts that had been present for several years. Due to worsening dyspnea and pulmonary cystic disease (image 1), she underwent a non-diagnostic VATS lung biopsy 3 years prior to consultation due to concern for LAM. Past medical history was notable for rheumatoid arthritis treated with adalimumab and leflunomide. Laboratory evaluation showed markedly elevated SSA and SSB antibody titers, which along with keratoconjuctivitis sicca and xerostomia was consistent with the diagnosis of Sjögren’s syndrome. The VATS lung biopsy was re-reviewed and showed atypical lymphoplasmacytic infiltrates with kappa light chain deposition, consistent with MALT lymphoma. Esophagogastroduodenoscopy and bone marrow biopsy were negative and staging PET-CT scan revealed no evidence of extrathoracic lymphoma. She was treated with weekly rituximab for 4 doses. DISCUSSION: Pulmonary MALT lymphoma is a rare disorder associated with autoimmune disorders, such as Sjögren’s syndrome. Extensive bilateral cysts are rare. Prognosis is typically good, although progression into high-grade B-cell lymphoma may occur. Treatment depends on symptoms and extent of disease. CONCLUSIONS: Pulmonary MALT lymphoma should be on the differential in patients presenting with bilateral extensive cystic disease. Image1: DISCLOSURE: Nothing to declare. KEYWORD: MALT Lymphoma