[Hodgkin's disease--an entity?].
Since 26 years Hodgkins disease is classified according to the Rye classification into 4 types. This classification is based on morphology and has turned out to be clinically relevant. However, sometimes the classification on morphological and immunohistochemical ground can be difficult to put a special case in a defined category of the 4 types. In addition, there seems to be no sharp, or well defined borders between Hodgkin's disease and Non-Hodgkin's lymphomas, especially T-cell lymphomas. Immunophenotyping of small lymphocytes and detection of follicular dendritic cells can demonstrate typical patterns in different types of Hodgkin's disease. In all types of Hodgkin's disease there is the same amount of proliferating small T-cells present. Hodgkin cells are lymphoid cells with B- or T-cell markers. Hodgkin cells of nodular para-granuloma (lymphocyte predominant type of Hodgkin's disease) show m-RNA for one light chain in the cytoplasm which can be visualized by in situ-hybridization. A new technique called "molecular histology" is applied to Hodgkin's disease. This is a single cell PCR of immunostained cells extracted from tissue sections by a micromanipulator. This technique enables us for the first time to demonstrate light chain and heavy chain gene rearrangements in Hodgkin cells of nodular sclerosis and mixed cellularity type. Hodgkin's disease seems to be no single entity but a heterogenous group of B- and possibly T-cell lymphomas. In the B-cell types Hodgkin cells are probably pre-B and B-cells.