In particular, according to our recent systematic review and meta-analysis of the published literature on the subject [5], out of 687 SNPs (located in 14 circadian genes) only 10 SNPs located in five genes (NPAS2 rs10165970, rs895520, rs17024869 and rs7581886; CLOCK rs3749474 and rs11943456; RORA rs7164773 and rs10519097; RORB rs7867494; and PER3 rs1012477) resulted in being significantly associated with the predisposition to only one tumour type, that is, breast carcinoma. This evidence concerns the gene PER3 and breast carcinoma.