ESR1 and cancer: Among unmodifiable factors, age (above 40 years), family history of cancer in first-degree relatives, hormonal profile (late menopause, early menarche), dense breast tissue, race and genetics (mutation in breast cancer susceptibility genes—BCRA1 and BCRA2 genes, TP53, genetic polymorphisms in genes encoding enzymes involved in estrogen metabolism pathways COMT, CYP1A1, CYP1B1, estrogen receptors ERα/ERβ, CYP17A1 and CYP19A1) are of great importance.