Morphology and classification of malignant lymphomas and so-called reticuloses

There is general agreement as to the definition and subclassification of Hodgkin lymphomas, which is acceptable for practical reasons. However, the nature of the different types of Hodgkin lymphomas needs further consideration. On the other hand, today we are as far from agreement on non-Hodgkin lymphomas as ever before. Earlier European and American classifications have now to be reconsidered in the light of modern concepts of experimental immunology. It has become necessary to apply immunochemical and immunomorphological methods in addition to histological, histochemical, cytological, and ultrastructural techniques. Only such a complex approach has been able to provide new insight into the functional properties of the tumor cells. The result was a new lymphoma classification, which conforms to LUKES' concept in many respects. It was fundamentally accepted by a group of European lymphoma experts and has been condensed and modified in order to be applicable by as many lymphoma centers as possible. It has received the name "Kiel Classification" 1974. The main principles of the classification are as follows: 1. A distinction is made between malignant lymphomas of low-grade and those of high-grade malignancy; "-cytic", "-blastic" m.l. 2. The terms "sarcoma" and "leukemia" are avoided. All types of malignant lymphoma can be leukemic, however with differnt frequencies. All B-cell lymphomas can also show a monoclonal immunoglobulin increase ("paraproteinemia") in the blood, mostly of IgM. So-called macroglobulinemia of Waldenström is therefore not itself an etity, but instead a clinical syndrome. It has been shown that so-called reticulosarcoma is derived from immunoblasts, not from reticulum cells or histiocytes. The group of reticuloses also needs reconsideration. The term "reticulosis" is cytologically incorrect in most cases. Otherwise it refers to a group of diseases which we do not yet understand.