Nipple discharge is common in women of child-bearing age, even when they are not pregnant or breastfeeding. Although nipple discharge is rarely a sign of a serious illness, unexplained discharge can be distressing. In men, however, nipple discharge is always abnormal.
What is nipple discharge?
Nipple discharge is fluid that escapes from one or both nipples either spontaneously or in response to breast stimulation. It can be clear and watery, milky-white, pus-like, yellow or bloodstained.
Common causes of nipple discharge
Many different factors can cause a spontaneous and persistent nipple discharge in women. It usually occurs in response to hormonal changes, for example it is normal to have clear, milky-white or yellow nipple discharge during early and late pregnancy which may persist afterwards.
Some of the most common causes of nipple discharge in women include:
- Intraductal papilloma. This is a wart-like growth that grows in the milk duct of the breast and is the most common cause of single duct bloodstained nipple discharge, usually in just one breast.
- Duct ectasia. With age, the milk ducts in the breasts become shorter, wider and harder. Duct ectasia is the most common cause of multi-duct thick, bloodstained or clear nipple discharge in women reaching the menopause.
- Mastitis or an abscess can cause pus-like nipple discharge.
- Prolactinoma is a benign pituitary gland tumour that causes over-production of prolactin, which stimulates breast tissue.
- Medicines. Some medicines such as antidepressants, antihypertensives and synthetic hormones can stimulate the pituitary gland to release prolactin and trigger nipple discharge. Women taking oral contraceptives or hormone replacement therapy are often affected.
- Breast cancer. A rare type of cancer called Paget’s disease of the nipple can cause nipple discharge. Only one breast is usually affected and the nipple discharge may be bloodstained. The nipple skin may appear red, dry and flaky like eczema. A non-healing ulcer is usually visible. Paget’s disease of the nipple can occur in men and women and usually affects those over age 50.
Nipple discharge: when to be concerned
Although nipple discharge is rarely due to a malignant condition, it is always a good idea to have any change in your breasts checked. The majority of causes of nipple discharge are benign and can be treated with medicines or preventative measures.
Investigating nipple discharge
Your doctor will take a detailed medical history, review any medications you are taking and perform a breast examination. The breast exam includes checking for signs of infection, swelling, dimpling of the skin and colour changes, crusting or ulceration around the nipple.
If there is no spontaneous discharge, your doctor may gently massage the area around the nipples to try to stimulate some of the fluid to be released. A sample of nipple discharge is then tested to determine the type of cells present and check for infection; this is called a nipple smear.
Further tests for nipple discharge
Your GP may also refer you to a breast specialist for the following additional tests:
- Blood tests are usually done to check prolactin and thyroid hormone levels. If hormone levels are high, you may have a CT or MRI scan to check the pituitary and thyroid glands.
- Mammogram or ultrasound scan can help to check the milk ducts.
- Needle biopsy. A sample of cells is collected from the affected area to determine the type of cells present and to rule out cancer.
- Ductogram is a detailed mammogram of the ductal system. Using a very small catheter, a contrast agent is injected into the opening that is releasing the discharge and a mammogram is taken.
- Ductal lavage involves placing a very small catheter into the affected duct, injecting fluid into it and then aspirating the fluid back out. The fluid is examined under a microscope for cancer cells.