In situ breast cancer and microchimerism.

Microchimeric cells of fetal origin persistent in the maternal circulation post-partum are associated with protection against invasive breast cancer. Here using quantitative genomic methods, we evaluated for the presence of male fetal microchimerism in buffy coat cells from women with a prior history of breast carcinomas in situ (CIS) and in healthy controls. Fetal microchimerism was detected in 75 of 88 controls (85%) and in 57 of 89 CIS patients (64%). The odds ratio for protection against non-invasive breast disease was 0.26 (95% confidence interval 0.12-0.56; p < 0.001 adjusted for age and body mass index). Similar to women with invasive breast cancer, women with CIS who are naturally at high risk for future invasive disease were deficient for fetal microchimerism. In addition to autologous anti-tumor immune responses, the maintenance of haploidentical microchimerism may impart an allogeneic edge in immunosurveillance.