Relevance of Ki‐67 expression in the classification of non‐Hodgkin's lymphomas: a morphometric and double‐immunostaining study

The proliferation of reactive and neoplastic cells was retrospectively assessed in 92 cases of non‐Hodgkin's lymphoma by morphometry using a double‐immunoenzymatic technique including surface markers and the monoclonal antibody Ki‐67. The findings were compared with the histological diagnosis. The overall Ki‐67 positivity is not always a good measure of the corresponding corrected values and therefore we recommend that a correction should be made for the total number of complementary lymphocytes in the tumour. Taking the macrophages and the Ki‐67 positivity of the reactive cells into account does not generally add any information. There was no difference in reactive cell content between follicular (counted within follicles) and diffuse lymphomas within the tumour areas. The value of the group mean for low‐grade follicular (nodular) lymphomas was significantly higher than that of diffuse low‐grade lymphomas, but not significantly different from that of intermediate‐grade lymphomas. High‐grade lymphomas exhibited significantly greater Ki‐67 positivity than those of intermediate grade. In 76% of the cases there was significant agreement between malignancy grade (low/intermediate malignant versus high malignant) at 45% corrected Ki‐67 counts.