Cerumen phenotype and proliferative epithelium in breast fluids of U.S.-born vs. immigrant Asian women: a possible genetic-environmental interaction.

To determine whether a genetic-environmental interaction exists between the breast, a modified apocrine gland, its secretions, and the genetic polymorphic phenotypes of wet and dry cerumen, we examined nipple aspirate fluid (NAF) for proliferative disease in 172 U.S.-born and immigrant Chinese and Japanese women. Cytologic evidence of proliferative epithelial cells (benign hyperplasia and/or atypical hyperplasia) was found in the NAF of 36 women (20.9%). A significantly higher incidence of proliferative epithelial cells was present in the NAF of U.S.-born than in immigrant Asian women (28.6% vs. 16.5%) (p = 0.05). A higher proportion of U.S.-born Asian women with wet cerumen than women with dry cerumen had proliferative epithelial cells in NAF: 39.3% vs. 20.0% (p = 0.08). No significant difference in NAF proliferative cells was found between immigrant women with wet and dry cerumen: 15.8% vs. 17.3%; p = 0.50. A strong association of proliferative epithelial cells and cerumen phenotype was found in parous U.S.-born women (wet = 47.6% vs. dry = 16.0%; p = 0.002). No significant association with wet and dry cerumen phenotype was found in parous immigrant women (wet = 12.2% vs. dry = 20%). These findings support the hypothesis that an apocrine genetic polymorphic trait differentially influences susceptibility of the breast to proliferative disease in Asian women born in environments presumed to be of high risk for breast cancer compared to women from low risk environments.