Relationship between c-erbB-2 immunoreactivity and thymidine labelling index in breast carcinoma in situ.

The relationship between the presence of the c-erbB-2 protein, demonstrated immunohistochemically with antibody 21N, and thymidine labelling index (TLI) has been studied in the in situ component of 70 cases of carcinoma of the breast. A significant association was found between high TLI and positive staining. Twenty of the 70 cases stained (29%) and of those that were stained 75% had a high TLI; 43% of those with a high TLI stained positively but only 14% of those with a low TLI stained positively. Strong correlations were seen between nuclear size and histological pattern and both 21N staining and TLI. The majority of carcinomas of comedo pattern with large nuclei were 21N positive and had a high TLI, whilst those with small nuclei and a predominantly cribriform/micropapillary appearance did not stain and had a low TLI. In tumours of mixed histological pattern there was less concordance between staining and TLI. The significance of these findings in relation to the biological behaviour of these tumours and their clinical management is discussed.