Breast cancer in women of Japanese and Caucasian ancestry in Hawaii.

A pathology review of breast cancers in Japanese and Caucasian women indicates more numerous in situ carcinomas in the Japanese. Carcinomas with uniform nuclei were also more numerous among Japanese. Japanese women showed more extensive lymphocytic infiltrates adjacent to their tumors than did Caucasian women, and also showed more conspicuous sinus histiocytosis in tumor-free lymph nodes. Fewer Japanese women had lymph node metastases and those with metastases were less likely to have three or more nodes involved. Of these differences only those relating to local invasion, nuclear grade, lymphocytic infiltration, and sinus histiocytosis were statistically significant, but the demonstrated differences are internally consistent with differences in breast cancer incidence and mortality in the two races. Since the two races share the same medical care system and similar environments, the basis of these differences is probably a genetic modulation of hormonal balance and/or immunologic response.