Why does breast cancer cause nipple discharge?

Milk ducts are small channels that open at the nipple. Abnormal tissue near a duct can disturb its lining or cause fluid to collect and escape. Discharge may come from one breast, one duct, or happen without squeezing. Its colour and consistency can vary, and discharge has many causes, including hormonal changes, medicines, infection, and benign duct problems. The appearance alone cannot determine the cause.

Arrange an assessment for new, spontaneous, one-sided, or bloody discharge, particularly when it continues or occurs with a lump or nipple change. Avoid repeated squeezing, which can keep the discharge going. Record its colour, whether it appears without touch, and any medicines or recent pregnancy-related changes to discuss at the appointment.

Seek prompt care for bloody discharge, a new lump, nipple inversion, skin changes, fever, increasing pain, or redness. Urgent review is appropriate if the breast becomes rapidly swollen or you feel seriously unwell.

Ask whether the discharge needs imaging or laboratory testing, what changes matter most, and how to monitor it while waiting for assessment.