Pulmonary Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma: A Diagnostic Dilemma.

Primary pulmonary lymphoma (PPL) is a rare clonal proliferation of lymphoid tissue confined to the lungs, representing only 0.5%-1% of all lung neoplasms. Pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma is the most common subtype and is often associated with chronic inflammation and autoimmune conditions. Diagnosis is challenging given its indolent course, nonspecific clinical features and variable radiographic presentations. We report a 64-year-old female with systemic lupus erythematosus who was incidentally found to have multiple pulmonary nodules. Serial imaging revealed interval growth and biopsy confirmed pulmonary MALT lymphoma. A watchful waiting strategy was initially employed, but subsequent disease progression prompted rituximab therapy, with only mild radiographic response despite preserved clinical stability. This case highlights the diagnostic challenges of pulmonary MALT lymphoma, the variability in treatment response and the potential interplay with autoimmune disease. Further studies are needed to clarify optimal therapeutic approaches, including the role of macrolides and autoimmune-directed therapies.