A combined morphologic and immunologic approach to the diagnosis of gastrointestinal lymphomas: I. Malignant lymphoma of the stomach (a clinicopathologic study of 22 cases).

Twenty-two cases of primary gastric non-Hodgkin's lymphoma, which occurred over a 20-year period, were reviewed. Eighteen tumors were studied using an immunoperoxidase method, and the presence of intracytoplasmic monoclonal immunoglobulin (Ig) in nine (50%) suggested a B-cell origin. Four tumors (22%) contained intracytoplasmic muramidase (lysozyme), suggesting a true histiocytic origin. Five tumors (28%) did not contain immunoglobulin or muramidase. The muramidase-positive "true histiocytic lymphoma" could not be differentiated from histiocytic lymphoma of lymphocytic origin using light microscopic examination alone. The patients with B-cell lymphoma survived significantly longer than patients in the other two groups. The differentiation between true histiocytic lymphoma and other conditions is discussed.