Comparison of Morphologic Features and Mitotic Rate to Cytometrically Determined DNA Content of Poorly Differentiated Lymphocytic Lymphomas

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Abstract
A direct correlation between the percentage of cells in S phase of the cell cycle and the clinical behavior of lymphocytic lymphomas of low, intermediate, and high grade malignancy has been described. The histopathologist has used the mitotic rate and other morphologic criteria such as size of cells and nuclear characteristics as predictors/indicators of the aggressiveness of a tumor. We compared the S phase values of 22 cases of poorly differentiated lymphocytic lymphoma (PDL) of the B cell type, using flow cytometric measurement of DNA content, to morphologic features and mitotic rate (MR). The 22 cases were divided into 3 histologic groups: nodular PDL composed of small, cleaved lymphocytes (11 cases); follicular mantle zone lymphoma and those of intermediate differentiation (6 cases); and "blastic" PDL (5 cases). In Group 1 there was excellent correlation of MR, percentage of cells in S phase, and proportion of large cells (transformed lymphocytes) per high power field (HPF). In Group 2, this correlation was not found between MR and percentage of cells in S phase in five of the six cases. The high S phase in this group did correlate with the large proportion of large cells found primarily in pseudofollicular proliferation centers and in remnants of true follicular centers. These cells may have a prolonged S phase and thus fewer mitoses were seen. In Group 3, although both MR and S phases were high, a direct correlation between them as noted in the Group 1 cases was not seen, but an excellent correlation of the high S phase and the number of blasts was present. The fact that three of the five patients in this group died rapidly (within less than 2 years of presentation) and the two survivors were experiencing rapid progression of disease, supports the concept that this group represents a clearly different, more aggressive subclass of PDL.