A Practical Approach to the Evaluation of Lymphoid and Plasma Cell Infiltrates in the Lung

Pulmonary biopsy specimens demonstrate varying degrees of infiltration by lymphoid cells and plasma cells, which may raise concern about involvement of a lymphoid or plasma cell neoplasm. Although paraffin section immunohistochemical stains and molecular genotyping studies are capable of assisting in the distinction between reactive and neoplastic infiltrates, it can be difficult to decide what studies to perform. This article describes a practical approach for the evaluation of lymphoid and plasma cell infiltrates in the lung through the identification of several key histologic features.