We have identified associations of SNPs in several core genes of the IL-12 signaling axis and BC risk in Puerto Rican women, including some that have been reported in other populations, such as IL12A, IL12B, IL12RB1, TYK2, JAK2 and STAT4. In the era of precision medicine and immunotherapy, having specific information on how inherited genetics modulates immune responses towards cancer is especially desirable. This evidence concerns the gene STAT4 and cancer.