Mitoses in non-Hodgkin's lymphomas. Frequency and prognostic relevance.

The frequency of mitoses was investigated in 279 lymph node biopsies from untreated patients with non-Hodgkin's lymphomas. The data were correlated with histological subtypes and survival time. It could be shown that the frequency of mitoses increases parallel to the amount of large tumor cells, except for lymphoblastic varieties. The proliferative activity was not influenced by a plasmacytoid differentiation. The nodules of follicular centroblastic centrocytic lymphomas revealed more mitoses than did the diffuse lymphomas of a similar grade of malignancy which shows that the growth pattern must be considered when the frequency of mitoses is interpreted. Immuno- and centroblastic lymphomas exhibited no marked differences with regard to mitotic activity. If all lymphomas are subdivided into three groups according to the mitotic grade alone, three survival curves are obtained that differ significantly from each other. It is concluded, therefore, that the mitotic activity of malignant lymphomas is a useful prognostic parameter that, until now, has received unduly limited attention.