Many things can stimulate breast tissue to produce fluid from the nipples.The breast is a secretory gland that responds to the stimulation of different hormones, including estrogen and progesterone. These hormones are responsible for controlling breast development during puberty. Estrogen promotes the growth of the ducts in the breast, whereas progesterone helps in the development of the secretory cells. The functional unit of the breast is called the terminal duct lobular unit (TDLU). Mammary secretions originate from these breast lobules. It is important to differentiate between nipple discharge and secretion of the nipple.Nipple discharge is defined as fluid that comes out spontaneously from the nipple. Nipple secretion refers to fluid that is present in the breast and comes out upon mechanical stimulation of the nipple and underlying ducts.It is normal for many women to express fluid using external pressure. A small amount of sticky, gray, green, serous, or black viscous fluid could be present. The patient who is curious to check for discharge may cause continuous mechanical stimulation and as a consequence, have production of fluid. Women are advised to avoid checking themselves for discharge since benign discharge may resolve when the nipple is left alone. Nipple discharge is the third most common complaint among women after breast pain or a breast mass. Up to 50% of women in their reproductive years can express one or more drops of fluid from the breast. Nipple discharge is seldom caused by a malignancy. Nevertheless, it does raise the concern about two uncommon but serious conditions. These are breast cancer and a pituitary tumor.Common Features:• Unilateral or bilateral discharge• Cycle variation • Induced or spontaneous discharge• Discharge may be clear, serous, milky, yellow, green, pink or slightly bloody, brown or black (old blood)• Discharge may originate from one or multiple ducts.Please call your plastic surgeon or primary care doctor.Best of luck,Mats Hagstrom, M.D.
