What was once a sure sign of consorting with devils, and now known in scientific circles as
galactorrhea : When non-nursing
women secrete or can
express a white, yellowish or green
discharge from one or both
nipples.
Milky discharge from breasts may be a sign of a benign growth in the pituitary gland known as a microadenoma (or prolactinoma) . While benign, tumors of this sort cause the pituitary gland to increase secretions of the mother's milk hormone prolactin and can cause false symptoms of pregnancy by interfering with normal menstrual periods. Benign pituitary microadenomas may also affect vision and may be a cause of temporary infertility. An endocrinologist will be able to diagnose, and, where necessary, treat these problems.
Other conditions associated with nipple discharge are infection of the Montgomery glands (those little zitty things on the aureolae), breast cancer, and pregnancy.
If you experience nipple discharge, call your doctor immediately. Obviously.