Purpose: Estrogen receptor (ER) expression is known as one of the major risk factors for breast cancer. Increased estrogen responsiveness of the breast epithelium may enhance this effect. We examined the relationship between breast cancers and
benign
breast diseases by using ER positive or negative expression and other established or possible risk factors. Methods: Using immunohistochemistry we measured ER expression in 33 breast tissues from benign breast diseases and 208 breast tissues from
breast
cancer. Data on established or possible risk factors, including age, age at menarche, age at 1st delivery, feeding methods, familial history of breast cancer, menopause status, hormonal replacement therapy, and oral pills, were collected prior to
surgery. Multiple logistic regression was used to assess the risks (odds ratios [ORs]) of the breast cancer based on ER-positive expression. Results: The positiverate of ER expression was higher in malignant breast tissues than in benign breast
tissues,
and it was related to breast cancer risk (p＜0.01). The crude OR for breast cancer in breast tissues which were ER positive versus those which were ER negative was 3.38 (95% confidence interval [CI]=1.32∼9.24) after adjusting for all factors,
and
each
OR for breast cancer was over 4.0 for such risk factors as older age on operation, postmenopausal women, age over 30 at 1st delivery, non-breast feeding, and familial history of breast cancer. Menarche was the exception. Conclusion: For early
detection
and for prevention of breast cancer we recommend carefully observation of benign breast disease patients with positive ER expression who are postmenopause, were over 30 at first delivery, did not breast feed, and had a familial history of breast
cancer
because the positive expression of ER in a benign breast epithelium may increase estrogen sensitivity and breast cancer risk.
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