Nipple discharge in non-lactating women can be classified as either galactorrhea or non-milky nipple discharge. Galactorrhea is usually caused by hyperprolactinemia and is associated with endocrine disorders or medication. Most of the causes of non-milky nipple discharge are benign, with less than 15% of cases related to cancer. The diagnostic approach is based on patient history and the characteristics of the discharge. Spontaneous, unilateral, and/or bloody nipple discharge, especially in women older than 40 years, should raise suspicion of malignancy. Treatment depends on the underlying disorder.
- Lactation: normal milk production in breastfeeding women
Galactorrhea: milk production in non-breastfeeding women or men 
- Discharge varies in color (clear, white, yellowish, or greenish)
- Expressed from either or both breasts
- Non-milky nipple discharge: production and secretion of fluids other than milk 
- Patient history
- One-sided and/or non-milky discharge
Signs that suggest malignancy
- Spontaneous, unilateral; , uniductal, and bloody, or guaiac-positive discharge
- Presence of a breast mass or abnormalities in imaging
- Age > 40 years
Biopsy is mandatory if malignant disease is suspected.
- Non-milky nipple discharge: : Treatment depends on the underlying disorder and can be found under respective causes (e.g., terminal ductal excision in the case of intraductal papilloma).