A pathologic study of benign breast diseases in Tokyo and New York.

Two hundred thirty-two biopsies of benign breast conditions from the National Cancer Center Hospital in Tokyo and 263 comparable biopsies from Memorial Hospital in New York City were reviewed. The component lesions of benign breast disease were identified and evaluated according to their relative frequency for different ages. Apocrine cysts, apocrine hyperplasia, intraductal hyperplasia, sclerosing adenosis, blunt duct hyperplasia, and atypical lobular hyperplasia were at least twice as common in biopsies from American women. Solitary papillomas were twice as common among biopsies from Japanese patients and tended to show more epithelial proliferation and sclerosing papillomatosis than did Americans. No major differences were found in the frequency of cysts, duct stasis, periductal mastitis, sclerosing intraductal papillomatosis, fibroadenomatoid mastopathy or fibroadenomas. Assuming intraductal hyperplasia and atypical lobular hyperplasia may represent premalignant epithelial changes, the high frequency of these lesions in New York biopsies when compared to Tokyo biopsies correlates well with the higher rate of breast cancer in the United States as compared to Japan. The greater frequency of lobular proliferative lesions and apocrine disease in New York suggests that these lesions may be produced by factors which also predispose American women toward breast cancer.