It has been reported that cytokines synthesized and released by tumor cells influence the surrounding fibroblasts, regulating their differentiation and stimulating both the aromatase expression and activity in them; melatonin at pharmacological concentrations (1 mM) counteracts this stimulatory effect, by inhibiting cytokines release from malignant cells (such as IL-6) and through the inhibition of the activity of aromatase [37, 38]. This evidence concerns the gene CYP19A1 and neoplasm.