Nipple discharge is a common breast symptom and one that can be particularly alarming when first discovered. There are many underlying causes of nipple discharge. The breast specialist’s job is to differentiate the serious underlying causes of nipple discharge from those that do not require any further evaluation. Benign conditions such as fibrocystic change, duct ectasia, and periductal mastitis can all create nipple discharge that emanates from both breasts and is generally
present from more than one duct. The discharge is usually cloudy and may be green, dark or gray. This type of discharge generally is present with manipulation of the nipple and occasionally can be stimulated by taking a shower.
Most nipple discharge is benign and not related to an abnormality. Discharge can range in color from white to yellow to green and even bluish green. This is known as physiologic discharge and is not associated with breast cancer. If the discharge is clear and thick, like mucus, this should be investigated as thoroughly as if it were bloody.
Milky discharge (cloudy, whitish or almost clear in color, thin, non-sticky) is the most common type of discharge. Most milky discharge is caused by lactation or increased mechanical stimulation of the nipple due to fondling, suckling or irritation from clothing during exercise or activity. Drugs or hormones that stimulate prolactin secretion can cause spontaneous, persistent production of milk (galactorrhea). Prolactin is the hormone produced by the pituitary gland that starts the growth of the mammary glands and triggers production of milk. Some pituitary tumors cause excess prolactin secretion that can lead to milky nipple discharge, usually from both breasts (bilateral). Opalescent discharge that is yellow or green in color is normal.
Most bloody or watery (serous) nipple discharge (approximately 90%) is due to a benign condition such as papilloma or infection. A papilloma is a non-cancerous, wart-like tumor with a branching or stalk that has grown inside the breast duct. Papillomas frequently involve the large milk ducts near the nipple. Multiple papillomas may also be found in the small breast ducts further from the nipple. Of the benign conditions that cause suspicious nipple discharge, approximately half is due to papilloma and the other half is a mixture of benign conditions such as fibrocystic conditions or duct ectasia (widening and hardening of the duct due to age or damage). Most opalescent discharge is due to duct ectasia or cyst. Suspicious nipple discharge is due to a malignant (cancerous) lesion just ten percent (10%) of the time. Discharge caused by a malignant condition is almost always on one side only (unilateral). Discharge that is coming from both breasts (bilateral) is usually benign. Papilloma usually causes discharge from a single breast duct.
A key question is whether the discharge is spontaneous, or whether it occurs only when the nipple is squeezed. It is less of a concern if the discharge occurs only when the nipple is squeezed, since most women can elicit discharge if they squeeze their nipple. If the discharge is spontaneous, rather than go to your internist or Ob/Gyn, you should consider going directly to see a breast specialist, meaning a surgeon who specializes in breast diseases. The specialist will perform a clinical breast exam and, if appropriate, a mammogram and an ultrasound. The discharge should also be examined to see if it contains blood. This is done with the same kind of test that is used to test for blood in stool. It should be done as part of the breast exam, as opposed to sending the sample to pathology. If the breast exam is negative, but the discharge tests positive for blood, a ductogram might be should be done. This is a procedure in which dye is inserted through the duct and then x-rays of the duct system are taken. A ductogram allows the surgeon to identify which duct system the bleeding is coming from and to determine whether there is a blockage in the duct that might be causing the discharge. (Think of a pipe that is rusty on the inside and gets blocked; when the rust breaks off it will come out the end of the pipe, making the water discolored). It is best to have the ductogram done at a breast imaging center that has experience in doing this type of breast x-ray. Some breast centers are also now doing ductal lavage (washing out the milk duct to look for abnormal cells) and even ductoscopy (threading a very tiny catheter into a milk duct through the nipple to see what is causing the discharge).
It is possible that the surgeon will find that you have an intraductal papilloma-a benign growth. This is most often identified by the presence of a spontaneous bloody nipple discharge. On rare occasions the discharge can be due to a precancerous condition called ductal carcinoma in situ (DCIS). But this really is rare. Only four percent of spontaneous bloody nipple discharge is found to be related to breast cancer. Even so, it is important and necessary to have the discharge examined by your physician.
It is also worth noting that smoking, hypertension, birth control pills, and some tranquilizers can influence nipple discharge because they stimulate prolactin, the hormone that influences lactation. So if you smoke, take the pill or tranquilizers, or have hypertension, you should mention this to the breast specialist.