[Classification of non-Hodgkin's lymphomas on the basis of Morphological and immunological features shared by normal and neoplastic lymphatic cells (author's transl)].

A review is given of the new Kiel classification of non-Hodgkin's lymphomas (NHL) and of the findings which led to its development. The Kiel classification of NHL is based on morphological and immunological features shared by normal and neoplastic cells. Therefore, the origin, maturation, and reaction of nonneoplastic T- and B-cells together with their immunological, enzyme-cytochemical and morphological features are discussed first. In the T-cell system T-precursor cells, prothymocytes, T1/T2-cells, and T-immunoblasts can be distinguished on the basis of the given features. The B-system is primarily composed of cells of the two antigen-dependent B-cell reactions, the germinal center reaction, and the plasma cell reaction. These cells can be distinguished both morphologically and through demonstration of the complement receptor in frozen sections. We differentiate the following entities of NHL, divided into six groups for better understanding: 1. lymphocytic lymphomas: chronic lymphocytic leukemia (CLL), prolymphocytic leukemia, hairy cell leukemia, mycosis fungoides, and Sézary syndrome; 2. secretory immunoglobulin-producing lymphomas: plasmacytoma and lymphoplasmacytoid immunocytoma; 3. germinal center cell tumors: centroblastic/centrocytic lymphoma, centrocytic lymphoma, centroblastic lymphoma, Burkitt's lymphoma, and lymphoma of the Burkitt type; 4. lymphoblastic lymphomas: "convoluted cell" type and "unclassified" type; 5. immunoblastic lymphoma; 6. reticulosarcoma. B-cell characteristics are revealed by more than 80% of the NHL, namely by 97% of the cases of CLL, by all secretory immunoglobulin-producing lymphomas, by all germinal center cell tumors, and by most immunoblastic lymphomas. More than 50% of the B-cell tumors are evidently derived from germinal center cells. The following are T-cell tumors: a few rare forms of CLL, mycosis fungoides Sézary syndrome, about 50% of the lymphoblastic lymphomas, and a few immunoblastic lymphomas. It could be shown that the cells of lymphoblastic lymphoma, "convolted cell" type with strong acid phosphatase reactivity have the same features as fetal thymocytes. So far, we have not observed any cases of true reticulosarcoma as described by Roulet and Rappaporti, i.e. tumors of phagocytic reticulum cells. The morphological features which could be defined for the entities distinguished in the Kiel classification of NHL are so characteristic that most of these entities can now be diagnosed on the basis of their histological and cytological pictures alone.