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.