Morphologic studies of lymphocyte nuclei in follicular and diffuse mixed small- and large-cell (lymphocytic-histiocytic) XXXX .

@entity1893 @entity1373 @entity706
Twelve examples of mixed small- and @entity706 (eight follicular, one follicular and diffuse, and three diffuse) were investigated morphometrically using plastic-embedded tissue in order to study nuclear characteristics of lymphocyte populations in this form of @entity1893 ( @entity1893 ) and to test morphologic bases for current @entity1893 classification systems. This study illustrates that there are many inaccuracies, illusions, and misconceptions in the morphologic criteria currently used to classify mixed small- and @entity706 . A principal finding was that lymphocyte nuclear profiles in @entity1893 tend to be smaller in size (P less than .005) and more irregular in shape (P = .0001) than the morphologically similar counterparts in germinal centers of lymph nodes with @entity1373 . Intercase comparison of mixed small- and large-cell lymphomas revealed a considerable range of mean nuclear area values, some of which were within the size range of normal, small lymphocytes. At the magnifications used for morphometric assessment, a high proportion of lymphocyte nuclear profiles had shallow invaginations, but only a limited number of profiles (4% to 14%) had deep (cleaved) indentations. Contrary to current definitions for this subtype of @entity1893 , lymphocytes with "small" nuclei had the same proportion of the nuclear diameter occupied by nuclear invaginations as lymphocytes with "large" nuclei and, in fact, mean nuclear invagination depth was shallower in "small" nuclei than in "large" nuclei. Furthermore, regardless of whether it is nuclear area or shape that is evaluated, lymphocytes in @entity1893 do not separate into two populations of small-cleaved and large noncleaved cells. Morphometry reveals that only four of the 12 examples of mixed small- and @entity706 had a proportion of the lymphocytes in the size range of fully transformed germinal center lymphocytes that exceeded 25%, and none of the cases approached 50% even though the population of lymphocyte nuclei appearing "transformed," and therefore "large," ranged from 28% to 57%. Such results indicate that the large, noncleaved and cleaved component, as seen in histologic sections of mixed small- and @entity706 , do not have nuclei of uniform size and many, in fact, are not actually large. The morphometric findings indicate reasons for the poor observer reproducibility in classifying this subtype of @entity1893 .
