Tumour cellularity, oestrogen receptors and prognosis in breast cancer.

One hundred and thirty-seven patients with operable breast cancer have been treated by mastectomy and node sampling. At the time of operation, portions of tumour were taken for determination of oestrogen receptor activity. In 91 cases adjacent tissue was taken for fixation and histological assessment of malignant epithelial cell content ('cellularity index'). The patients were followed for two years or more, or until first recurrence or death. Prognosis (probability of staying disease-free) was significantly better in patients whose tumours contained receptors than in those whose tumours were receptor-negative (p less than 0.03). However, the best prognosis was in patients with low receptor positive tumours. Those with highest values had a prognosis almost as poor as patients with receptor-negative tumours. In addition, a new finding emerged: prognosis was better in patients with tumours of low cellularity than in those with tumours of high cellularity (p less than 0.04). Since, for receptor-positive tumours, receptor level was also significantly correlated with cellularity (R = +0.35, p less than 0.01), the relationship between prognosis and receptor level was re-examined after 'correction' of the latter quantity for differences in cellularity: on this basis, again prognosis was better in patients with receptor-positive tumours (p less than 0.02), but there was no longer a tendency for any one sub-group of patients with receptor-positive tumours to fare better than the rest. It is concluded that prognosis in operable breast cancer is related to oestrogen receptor activity (either per mg weight, or per cell) and to cellularity.