Ultrastructural morphometry and the control of lymphocyte nuclear size in non-Hodgkin lymphoma: a review

Morphologic features, particularly nuclear characteristics, continue to be a major factor in the classification of the subtypes of non-Hodgkin lymphoma (NHL). Information is limited or nonexistent, however, concerning the mechanisms responsible for nuclear appearance. This is particularly true for nuclear size. In determining which of the nuclear compartments--condensed chromatin or the interchromatinic (euchromatin or nuclear matrix) region--is responsible for nuclear size, ultrastructural morphometric analysis has been a useful tool. Linear regression analysis has been used to compare, in turn, condensed chromatin area (CCA) and interchromatinic area (ICA) against nuclear area (NA). Whether in normal or neoplastic lymphocytes, correlation coefficients are moderately good when CCA is matched against NA, but CCA is only a weak predictor of NA. In contrast, correlation coefficients are remarkably high for ICA compared to NA, and ICA predicts NA to the degree of 94% to 97%. This holds true for all NHLs tested and for reactive hyperplasias. Despite abnormalities in lymphocyte nuclear size in NHL, the size of any nucleus is controlled by the amount of interchromatinic material to an exceptional degree. Even so, the mechanisms responsible for major changes in nuclear volume during transformation of normal lymphocytes are apparently altered in NHL. Morphometric analysis, ultrastructurally, can assist in understanding, testing, and defining diagnostic morphologic criteria in this disease.