Description of non-Hodgkin lymphoma. I-low-grade lymphoma diffuse lymphocytic, well-differentiated; nodular lymphocytic, poorly differentiated; nodular mixed lymphocytic-histiocytic. II-intermediate-grade lymphoma nodular histiocytic; diffuse lymphocytic, poorly differentiated; diffuse mixed lymphocytic-histiocytic; diffuse histiocytic. III-high-grade lymphoma histiocytic; diffuse undifferentiated