Morphological classification of malignant lymphomas: ultrastructural, cytochemical and immunological results.

Except for tumors clearly producing immunoglobulin (e.g. plasma-cytoma), the different classes of malignant lymphomas do not correlate with a constant surface immunoglobulin pattern. Beside a prevailing IgM-surface type in a high number of different lymphoma classes even T-like or O-cells occur in most tumor types provided they are studied in a sufficient number. The possibility of dedifferentiation of immunologic cell qualities has to be envisaged. In this context intracellular lambda-chain crystals occurring in chronic lymphocytic leukaemia may provide a morphological hallmark of anaplastic deterioration of immunoglobulin synthesis. - The ambiguous significance of PAS-positive inclusions and virus-like microtubular complexes in lymphoma cells is discussed. - In conclusion the recent discovery of hairy cell leukaemia provides a good example of the value of nomenclatures based on empiricism rather than on short-lived theories.