Proliferation indices in spontaneous canine lung cancer: Proliferating cell nuclear antigen (PCNA), Ki-67 (MIB1) and mitotic counts

Proliferation indices were measured for specimens from 55 spontaneous canin e lung tumours, collected by surgical biopsy from clinical patients and arc hived in paraffin wax blocks. These indices were then related to the mitoti c index and histological type of the tumour. Proliferating cell nuclear ant igen (PCNA) and Ki-67 (MIB1) proteins were detected immunohistochemically w ith a biotin-streptavidin amplified detection system on a representative ti ssue section from each tumour. Five adjacent, non-overlapping fields were s elected at random, and 200 cells per field were examined in each section. F or PCNA, cells were classified subjectively into negative, weak or strong r eactivity groups, based on nuclear staining. MIB1 cells were classified as negative or positive, based on nuclear staining. Mitotic figures were count ed in anti-PCNA-labelled and anti-MIB1-labelled sections, in the same tumou r areas as those in which indices were established. Mitotic counts were als o done on haematoxylin and eosin-stained tissue sections. Linear regression analysis showed that all PCNA, MIB1 and mitotic indices had highly signifi cant positive correlations (P < 0.0001) with each other. Adenosquamous and squamous cell carcinomas differed from other histological tumour types in h aving significantly higher proliferation indices. These data suggest that g rowth rates for lung rumours in the dog vary according to histological type . On the basis of differences in proliferation indices and the distribution of immunoreactivity between histological subtypes in this study; it would seem that immunohistochemical detection of PCNA and MIB/1 reactivity and an alysis of mitotic figures in routinely processed tissues may be useful in t he diagnosis of lung tumours. (C) 1999 W.B. Saunders Company Limited.