Nuclear areas in breast cancer: relationship with estrogen and progesterone receptor expression

The relationship between nuclear area and the expression of estrogen (ER) and progesterone receptors (PR) was evaluated in a series of 66 breast carcinomas (50 primaries, 16 metachronous recurrences). Nuclear measurements were directly performed on touch imprints previously reacted for ER and PR by the immunocytochemical method. Nuclei expressing ER or PR were found to be smaller than negative ones. Moreover, area values of PR+ nuclei overlapped with those of ER+ ones. The pattern of receptor expression co-existence was observed to be closely related to nuclear dimensions, since a significant increase in mean nuclear areas was detected in cells from ER-/PR-tumours, as compared with cells from ER+/PR+, ER+/PR- and ER-/PR+ sub-groups. Nuclear area values were also determined in both steroid receptor-positive and steroid receptor-negative neoplastic cells co-existing in the same breast carcinoma. No significant differences in nuclear area values were found between receptor-positive and receptor-negative neoplastic cells in tumours featuring a positive status for at least one of the steroid receptors (ER+/PR+, ER+/PR- or ER-/PR+). On the contrary, in breast carcinomas characterized by a negative steroid receptor status (ER-/PR-), receptor-negative neoplastic nuclei were significantly larger than receptor-positive ones. It is suggested that heterogeneous steroid receptor expression may be caused by a completely different pathogenetic mechanism in receptor-positive and receptor-negative breast carcinomas.