Lambert Skoog

Assessment of cell proliferation by Ki‐67 staining and flow cytometry in fine needle aspirates (FNAs) of reactive lymphadenitis and non‐Hodgkin's lymphomas

This study was undertaken to assess cell proliferation in FNAs from a series of 57 non‐Hodgkins lymphomas (NHL) and 11 cases of reactive lymphadenitis using Ki‐67 staining and flow cytometry (FCM). The results were compared and correlated to the cytomorphological subgrouping according to Kiel classification. The mean percentages of Ki‐67 positivity were 16.6% and 61.1% for low and high grade lymphomas, respectively (P < 0.001). The mean S‐phase fraction (SPF) determined by FCM was 4.6% for low grade and 12.9% for high grade lymphomas (P < 0.001). The figures for Ki‐67 positivity and S‐phase fraction in reactive lymphadenitis were 16.8% and 4%, respectively. We observed a strong correlation in low grade lymphomas between Ki‐67 and SPF. A good correlation was also found in reactive lymphadenitis. In high grade lymphomas, however, with highly scattered Ki‐67 and S‐phase values, this correlation was lost. In some cases this discrepancy can be explained by a rich admixture of non‐neoplastic, non‐proliferating cells in aspirates from diploid tumours. In addition, the existence of a minor aneuploid tumour cell population of high proliferation such as that in Ki‐1 lymphomas will not be accurately analysed by FCM but is easily assessed by Ki‐67 staining. However, the main reason seems to be a high variability between the fraction of cells in S‐phase and the total number of cells in G1, S and G2 in individual tumours.