Diffuse centrocytic and/or centroblastic malignant non-Hodgkin's lymphomas: comparison of mitotic and pyknotic (apoptotic) indices.

Mitotic indices (MIs) and pyknotic (apoptotic) indices (PIs) were assessed in diffuse centrocytic (CC, n = 10), centroblastic/centrocytic (CB/CC, n = 18) and centroblastic (CB, n = 20) malignant non-Hodgkin's lymphomas (NHL). Significant differences were observed. MIs were lowest in CC (median: 0.07%), intermediate in CB/CC (0.18%) and highest in CB (0.43%) NHLs. The PIs exhibited a similar pattern. The PIs of CC (0.11%) and CB/CC (0.17%) NHLs were significantly different from those of CB lymphoma (0.62%). The ratios MI/PI per case, as well as MIs and PIs per case, varied greatly and showed considerable overlapping, thus documenting a marked inter-case and inter-group heterogeneity. MIs tended to loosely correlate with PIs in a non-linear fashion, which raises the question of feedback mechanisms. More information is needed on mitotic time (TM) and apoptotic time (TA), in order to estimate cell doubling time from data on MIs and PIs.