Comparison between the monoclonal antibodies Ki‐67 and PC 10 in 125 malignant lymphomas

The monoclonal antibody (MAb) Ki‐67 detects a nuclear proliferation‐associated antigen which corresponds to a non‐histone protein with a molecular weight of 395 and 345 kD. Its prognostic relevance has been assessed in both lymphoid and non‐lymphoid tumours. The MAb PC10 picks up the proliferating cell nuclear antigen (PCNA), which is a 36 kD nuclear protein associated with the cell cycle Whereas Ki‐67 works only in fresh material. PC10 detects a fixation‐resistant epitope of PCNA. Preliminary data have revealed a linear relationship between Ki‐67 and PC 10 reactivity in normal lymphoid tissue and in non‐Hodgkin's lymphomas (NHLs). We applied Ki‐67 and PC 10 to frozen and routine sections, respectively, from 25 examples of Hodgkin's disease (HD) (14 nodular sclerosis, 6 lymphocyte predominance, 5 mixed cellularity) and 100 NHLs (corresponding to the main varieties of the updated Kiel classification). The results obtained can be summarized as follows: (1) both MAbs gave rise to extremely variable results within the same category of NHLs; (2) most Hodgkin and Reed‐Stern berg cells (50‐98 per cent) were labelled by the reagents; (3) Ki‐67 and PC10 stained a similar ratio of neoplastic cells in 65 and 76 per cent of NHL and HD cases, respectively; in the remaining instances, no correspondence was observed, the PC10‐positive elements usually outnumbering the Ki‐67‐positive ones significantly. These discrepancies, which might be due to low PCNA catabolism and/or PCNA expression by quiescent cells, underline the need for further kinetic and clinico‐pathologic studies in order to define the specific relevance of PC 10. Copyright © 1993 John Wiley & Sons, Ltd.