Primary pulmonary lymphoma (PPL) is a rare disease with a favorable prognosis compared with lung cancer. Although a number of histologic variables of B- and T-cell lymphoma were reported as PPL, marginal zone lymphoma of the mucosa-associated lymphoid tissue type is by far the most frequent diagnosis. This review summarizes the present knowledge of histopathology, molecular biology, diagnosis, prognosis, and treatment of this heterogeneous entity.