Nipple discharge is fluid that comes from one or both nipples.
 

Normal Lactation — Milk production normally occurs during pregnancy and breastfeeding and may continue for months after breastfeeding has stopped. Small amounts of milk can sometimes persist for a year or longer, particularly with continued nipple stimulation.
 

Galactorrhea — Milky nipple discharge unrelated to pregnancy or normal breastfeeding. It is usually bilateral and from multiple ducts and may occur spontaneously or with expression. It is often associated with elevated prolactin, which can result from medications (especially certain psychiatric medications), hypothyroidism, pituitary tumors, pregnancy, nipple stimulation, marijuana use, and other causes. Evaluation commonly includes a pregnancy test, prolactin level, TSH, and medication review when appropriate.
 

Non-Milky Discharge — Non-milky discharge can be benign or, less commonly, cancerous. Spontaneous, unilateral, single-duct, clear/serous, or bloody discharge is more concerning and generally requires diagnostic breast imaging. For patients younger than 30, targeted breast ultrasound is generally the initial imaging test. For patients age 30 and older, diagnostic mammography and targeted ultrasound are generally appropriate. Most cases still have benign causes, such as intraductal papilloma or mammary duct ectasia, but additional imaging and sometimes biopsy may be needed to determine the cause and exclude malignancy.

Breast Cancer
 

Most nipple discharge is not caused by cancer, but malignancy must be considered when discharge has suspicious features:
 

• Spontaneous unilateral discharge

• Persistent single-duct discharge

• Bloody or clear/serous discharge

• A new breast mass

• New nipple inversion or distortion

• Nipple ulceration

• Eczematous or crusting nipple changes

• Skin dimpling or other suspicious breast changes

• Enlarged or abnormal axillary lymph nodes

                                                         References & Guidelines
 

• American College of Radiology (ACR). Appropriateness Criteria: Evaluation of Nipple Discharge.

• American College of Radiology (ACR). Appropriateness Criteria: Breast Imaging During Pregnancy and Lactation.

​