Breast cancer and prognostic factors. Tumour size, degree of differentiation, proliferation kinetics and expression of steroid hormone receptors.

In a group of 161 patients with operable cancer of the breast, tumour size, axillary node status and histopathological grading were correlated. Furthermore, steroid hormone receptor status was assessed both biochemically and immunohistochemically. The rate of Ki67-positive cells, the ploidy status and the S-phase fraction of the carcinoma, as assessed by means of flow-cytometry, were measured and correlated with tumour size and conventional histopathological grading. As expected, a significant correlation between tumour size and the frequency of axillary lymph node metastases was found (p < 0.00001). There was however, also a significant increase of undifferentiated cancers with increasing tumour size (p < 0.001). There was no correlation between steroid hormone receptor expression and grading but a slight decrease of immunohistochemically oestrogen receptor positive cancers with increasing tumour size (p < 0.02). On the other hand, there was a marked increase of both Ki67-score (p < 0.003) and S-phase fraction (p < 0.001) with increasing tumour size. Neither of the first two parameters correlated significantly with grading. The frequency of aneuploid tumours was dependent on tumour size (p < 0.05) as well as grading (p < 0.01). The findings point towards a change of biological properties of the cancer during the course of growth, such as histopathological dedifferentiation and increased proliferation fraction and frequency of aneuploid tumours. The expression of steroid hormone receptors however is virtually unchanged.