Primary pulmonary MALT lymphoma with probable isolated light chain deposition disease: Case report and literature review

Primary pulmonary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is an uncommon lymphoproliferative disorder with variable imaging manifestations that may overlap with infectious, inflammatory, and neoplastic processes. Light chain deposition disease (LCDD) is a rare monoclonal immunoglobulin deposition disorder that may occur in association with indolent B-cell lymphoproliferative disease, although isolated pulmonary involvement remains uncommon. We present the case of a 39-year-old woman initially found to have numerous bilateral pulmonary, hilar, and mediastinal nodules, many demonstrating eccentric calcifications, which raised concern for metastatic disease in the setting of a prior malignancy. Multiple biopsies were initially inconclusive, and serial imaging over several years demonstrated progressive ground-glass and multiseptated cystic changes; subsequent biopsy of an enlarging left lower-lobe lesion, together with molecular evidence of clonal immunoglobulin light-chain gene rearrangements, established the diagnosis of pulmonary MALT lymphoma. Following systemic therapy, surveillance imaging demonstrated development of new peripheral soft-tissue nodular components along several pre-existing cystic lung lesions, highly suggestive of superimposed kappa light chain deposition disease. This case highlights the uncommon association between pulmonary MALT lymphoma and LCDD and showcases the evolving radiologic appearance of these processes over prolonged follow-up. Recognition of cystic change and calcified or cyst-associated nodules in patients with pulmonary MALT lymphoma may suggest an associated light chain deposition disorder and prompt appropriate radiologic-pathologic correlation.