Primary nodular lymphoma of the lung. Immunoperoxidase and ultrastructural studies

In two patients, primary nodular lymphomas of the lung which presented incidentally were diagnosed following routine chest radiography, exploratory thoracotomy, and the application of histologic criteria. The diagnoses were confirmed using the peroxidase-antiperoxidase (PAP) technique and transmission electron microscopy. Whereas most investigators had demonstrated intracytoplasmic immunoglobulins in only the large cells of nodular lymphomas using the standard PAP method, we were able to prove the presence of monoclonal immunoglobulin within the cytoplasm of both the large cells and small cells using a modification of the PAP technique as described by DeLellis. This modification uses very dilute antisera and a prolonged incubation time and is more highly sensitive and specific. Monoclonal immunoglobulin was also shown to be within the cytoplasm of mature plasma cells observed within the interfollicular areas. This monoclonal immunoglobulin was the same as that seen within the cytoplasm of the small and large cells of each respective lymphoma. Electron microscopy permitted the identification of three cell types within each patient's tumor: small cells, large cells, and dendritic reticulum cells((DRCs). The finding of the DRCs, presently considered a residual marker of the germinal center, is supporting evidence that both lymphomas studied were nodular lymphomas of B cell derivation.