The pathology of breast cancer in Japanese women compared to other ethnic groups: a review.

Review of comparative pathology studies of breast cancer among Japanese women and other ethnic groups reveals consistent differences in tumor morphology and host response. Japanese women show lower rates of breast cancer than Caucasian women, a difference that is accounted for by increased rates of this cancer in postmenopausal Caucasian women. Postmenopausal breast cancer is also less common among Japanese who migrated to a western environment. Autopsy studies of Japanese women without breast cancer indicate a lower prevalence of ductal hyperplasia, a breast cancer precursor, among indigenous Japanese women and first generation migrants than among second generation Japanese women in Hawaii who have higher rates of breast cancer. Postmenopausal breast cancers in Caucasian women are more likely to have estrogen receptors than cancers in postmenopausal Japanese women or premenopausal women of either race. Postmenopausal Japanese women are more likely to have in situ tumors than Caucasian women, even after adjusting for tumor size. A more vigorous host response to breast cancer among Japanese women, as compared to Caucasians, is suggested by more intense lymphocytic infiltration, greater degrees of lymph node sinus histiocytosis and fewer lymph node metastases in the Japanese.