Primary pulmonary marginal zone lymphoma: an unusual cause of pulmonary infiltrates.

Primary pulmonary extra-nodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), also known as bronchus-associated lymphoid tissue (BALT lymphoma), is the most common primary pulmonary lymphoma but is rare (<1%) among all non-Hodgkin lymphomas and among pulmonary neoplasms in general. We herein report the case of a 59-year-old male who presented with stable exertional dyspnoea and persistent lung infiltrates who was referred to our hospital for further assessment. A computed tomography (CT)-guided core biopsy was performed showing a dense lymphoid infiltrate, with further testing revealing the diagnosis of pulmonary MALT lymphoma. This uncommon lung tumour is usually seen in older adults and typically associated with a relatively indolent course. Rituximab, an anti-CD20 antibody, has been shown to be effective in up to 70% of cases.