Working formulation of the non‐Hodgkin's lymphomas: A study of cell size and mitotic indices in cytologic subtypes

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Abstract
Cell size and mitotic indices were studied in 243 nonHodgkin's lymphomas (NHL) diagnosed cytologically and classified according to the Working Formulation. Low-, intermediate-, and high-grade lymphomas constituted 14.8%, 18.9%, and 61.7% of the cases, respectively. Measurement of the diameter of 100 lymphoid cells in each case showed that in most of the low-grade malignant lymphomas, 50-80% of the cells were small (< 10 μm). A majority of the cells (an average of 45-60%) in intermediate- and high-grade lymphomas were in the range of 11-15 μm. Only the intermediate-grade large noncleaved and high-grade immunoblastic lymphomas had a majority of their cells (> 50%) larger than 15 μm. The mitotic indices (number of mitotic figures per 500 lymphoid cells) showed a highly significant difference between low- (0.7±1.14), intermediate- (3.0±2.67), and high-grade (5.4±3.40) lymphomas using the Wilcoxon's signed rank test (P < 0.0001). Nearly two-thirds of the cases in each grade were within specific ranges of mitotic indices, i.e., < 1 for low-, 1-3 for intermediate-, and > 3 for high-grade lymphomas.