Menopausal status, adipose tissue, and breast cancer risk: impact of estrogen replacement therapy.

The seeds of breast cancer are likely sown in the first two or three decades of life. Rapid weight gain and height in infancy predict breast cancer risk in later life. The age at first pregnancy is also a strong predictor for breast cancer; the earlier the first full-term pregnancy, then the lower the risk of breast cancer in later life. It has been postulated that the breast stem cell number may be the factor linking these observations together. Menopause, per se, is associated with an increase in central adiposity, which is reversed by hormone replacement usage. Breast and nonbreast fat both produce estrogens and cytokines that may promote the growth of small breast cancers making them appear earlier. Obesity also is associated with metabolic syndrome, which is a risk factor for breast cancer. The breast cancer stem cells make up only around 1%-2% of the tumor mass and, yet, are the likely driver for much of a breast cancer's behavior. Future research into breast cancer biology, especially into the cancer stem cells is likely to translate into novel methods of treatment and prevention of this common cancer.