Estrogen is associated with many epidemiologic risk factors for invasive breast cancer. Cells that express estrogen receptors (ERs) in epithelial hyperplasia lacking atypia (EHLA) may influence breast cancer progression. We conducted a nested case-control study of 268 women with biopsy-confirmed EHLA to determine whether immunohistochemical expression of ERalpha in EHLA affects subsequent breast cancer risk. Study subjects could not have a prior or current history of breast cancer or atypical hyperplasia. Immunohistochemical stains in individual lesions and adjacent normal lobules were considered positive if >or= 10% of epithelial cells stained for ERalpha. The risk of invasive breast cancer in EHLA patients with ERalpha-positive normal lobules was twice that of other EHLA patients (95% CI = 1.0-3.8). This risk was not affected by the ERalpha status of EHLA lesions. ERalpha expression in adjacent normal lobules increases the moderate breast cancer risk previously associated with EHLA.
(c) 2004 Wiley-Liss, Inc.