Formal discussion of Robert J. Lukes' paper, "Criteria for involvement of lymph node, bone marrow, spleen, and liver in Hodgkin's disease.

points of differentiation are reevaluated. For appreciation of the essential morphological features by pathologists. continued use of our original six histological types is recommended, since the four histological types of the Rye classification, although valuable for clinicians, do not convey morphological connotations. The significance of the Reed-Sternberg (R-S) cell variants are reviewed, with emphasis on the fact that the diagnostic R-S cell is only one of a wide variety of R-S variants. Three major problems involving morphological criteria have arisen from limited appreciation of (a) the R-S variants; (b) the identification of the variants of nodular sclerosis; and (c) the precise criteria for differentiating lymphocytic and histiocytic types, mixed and diffuse fibrosis types, and reticular types. The two original criteria for recognition and identification of nodular sclerosis, i.e., lacunar type R-S cells and wide collagen bands, are regarded as the most effective basis for classifying nodular sclerosis, although the distinctiveness of lacunar cells suggests the possibility of reliable identification of nodular sclerosis in a cellular phase without collagen bands. Recognition of the lymphocytic and histiocytic types (lymphocyte predominance) and diffuse fibrosis and reticular types (lymphocyte depletion) is not based simply on the number of lymphocytes but primarily on the character and frequency of R S cells or the type of fibrosis. The mixed type (mixed cellularity) serves both in an intermediate position between the two extremes and also as an unclassified type for those lesions that are not readily classifiable.