A case of non-Hodgkin's lymphoma of the esophagus in a 74 year old man is presented. Grossly, the surgically removed esophagus had a fusiform submucosal mass covered with smooth surfaced mucosa. Microscopic examination revealed that the mass consisted of a dense infiltrate of small to medium-sized lymphoid cells with plasmacytoid differentiation, leading to a diagnosis of diffuse small cell lymphoma with lymphoplasmacytic subtype. Laboratory data as well as immunohistochemical studies proved that the lymphoma produced monoclonal immunoglobulin M, giving rise to macroglobulinemia.