Correlation of erbB-2 gene amplification with low levels of estrogen and/or progesterone receptors in primary breast cancer: do erbB-2 products delineate hormone-independent tumors?

We analyzed erbB-2 gene amplification in 170 primary breast carcinomas. Thirty-one percent of tumors exhibited additional copies of erbB-2 gene. Chi-square analysis did not elicit any association between gene amplification and either menopausal or node status. A slight trend was observed with respect to the SBR grading. In contrast, significant correlation was associated with the age of patients and we found a strong relation with the intratumoral steroid receptor status. ErbB-2 amplification significantly occurs in tumors whose estrogen receptor and progesterone receptor were below the cut-off value or absent and tumors with dissociated estrogen receptor and progesterone receptor status were revealed as entities similar to both estrogen receptor and progesterone receptor negative tumors.