Abstract Introduction Primary pulmonary lymphomas (PPLs) are rare, accounting for only 0.5-1% of lung neoplasms, and most often occur in adults aged 50-60 years. Mucosa-associated lymphoid tissue (MALT) lymphoma, the most common subtype, frequently mimics infection, leading to diagnostic delay and repeated antibiotic exposure. Description A 60 year old man with no prior lung disease or smoking history initially presented with multifocal pneumonia. CT chest showed bilateral peribronchovascular and lobar consolidations, most prominent in the right middle and left lower lobes. Despite multiple antibiotic courses over several months, his symptoms and imaging failed to improve. Bronchoscopy with BAL and transbronchial biopsy were performed and revealed an atypical small B-cell proliferation positive for CD20, CD79a, Bcl-2, and CD43, and negative for T-cell and mantle markers, consistent with MALT lymphoma confirmed on tertiary pathology review. He subsequently completed six cycles of bendamustine-rituximab therapy. Nearly a year after his initial diagnosis, surveillance CT scans demonstrated residual pulmonary nodules that had decreased in size but remained mildly FDG-avid, prompting re-evaluation. A repeat bronchoscopy was performed to assess for alternative or infectious etiologies, and tissue examination revealed only scar tissue and entrapped reactive epithelium with no evidence of malignancy or infection. Given the absence of active lymphoma, he was treated with corticosteroids for post-inflammatory lung disease. On follow-up more than a year later, he remained clinically stable with mild exertional dyspnea and interval radiographic improvement. Discussion Primary pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma is a rare, indolent B-cell neoplasm that can resemble infection or organizing pneumonia on imaging. Previous reports(Rechal et al.; Parekh et al.) have described patients repeatedly treated for presumed non-resolving pneumonia before the correct diagnosis was made, sometimes for up to a decade. Similarly, our patient presented with persistent bilateral consolidations unresponsive to antibiotics, and the diagnosis was confirmed only after bronchoscopy with immunohistochemical analysis demonstrating MALT lymphoma. Re-evaluation of persistent FDG-avid pulmonary lesions with repeat biopsy later revealed only post-inflammatory changes, emphasizing the importance of reassessing apparent disease persistence to avoid unnecessary prolonged chemotherapy. This case demonstrates the value of early tissue diagnosis in non-resolving pneumonia, particularly in older adults without identifiable infectious or exposure risk factors. This abstract is funded by: None
Shaikh et al. (Fri,) studied this question.