Since our results show an inverse association with linoleic acid, a borderline positive association with serum levels of dihomo-γ-linolenic acid, and no relationship with arachidonic acid, the FADS2 desaturation index (indicator of Δ6-desaturase activity) was positively related to BC, while the FADS1 index (indicator of Δ5-desaturase expression) showed an inverse association. This evidence concerns the gene FADS2 and breast cancer.