CYP19A1 and breast carcinoma: Further evidence of imbalance in estrogen homeostasis derives from the greater expression of estrogen-protective enzymes, COMT and NQO1 (Fig. 2), in women without breast cancer and greater expression of estrogen-activating enzymes, CYP19 and CYP1B1 (Fig. 2), in breast tissue of women with breast cancer [82].