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Nipple Discharge: Causes, Warning Signs, Tests & Treatment

  • Prof. Dr. Zahid Mahmood
  • August 11, 2026

Nipple Discharge: Causes, Warning Signs, Tests & Treatment

Medically reviewed by Prof. Dr. Zahid Mahmood, MBBS, FCPS — General, Laparoscopic & Laser Surgeon, Lahore.

Nipple discharge is fluid coming through one or more milk-duct openings in the nipple. It is common during pregnancy and breastfeeding and is often caused by a benign condition. However, spontaneous discharge from one breast—especially from a single duct or when clear or bloody—requires proper breast assessment because an intraductal papilloma, duct abnormality or breast cancer can occasionally be responsible.

Colour alone cannot diagnose the cause. The most useful clues are whether the discharge occurs by itself or only after squeezing, whether it comes from one or both breasts, and whether it comes from one duct or several.

Physiological and pathological discharge

Features usually suggesting physiological discharge

  • Occurs only when the nipple is squeezed
  • Comes from both breasts
  • Comes from several duct openings
  • May be milky, yellow, green, brown or mixed in colour
  • No lump, skin change or newly inverted nipple

Repeatedly squeezing the nipple can maintain discharge by stimulating the ducts. Stop checking it repeatedly and arrange medical advice if it persists.

Features suggesting pathological discharge

  • Occurs spontaneously without squeezing
  • Comes from one breast
  • Comes from a single duct opening
  • Is clear, watery, serous or bloodstained
  • Stains clothing or recurs persistently
  • Occurs with a breast lump, nipple retraction or skin change

Pathological does not mean cancer. Most cases still have a benign explanation, but imaging and sometimes biopsy are needed.

Common causes

Pregnancy and breastfeeding

Milk or colostrum discharge is normal during pregnancy and lactation and can continue for some time after breastfeeding stops. A small amount of blood can occasionally arise from increased blood flow or nipple trauma, but persistent one-sided bleeding, a lump or skin change still needs ultrasound and clinical review.

Intraductal papilloma

An intraductal papilloma is a small benign growth inside a milk duct, usually near the nipple. It commonly causes spontaneous clear or bloody discharge from a single duct. Ultrasound may identify it, and a needle biopsy or removal may be advised to confirm the diagnosis and exclude atypical or malignant change.

Duct ectasia

Duct ectasia means widening of the major ducts behind the nipple. Thick secretions and inflammation can cause green, brown, black or toothpaste-like discharge, nipple retraction and tenderness. It becomes more common with age and is associated with smoking and periductal inflammation.

Mastitis or breast abscess

Infection can cause pus-like discharge with breast pain, redness, warmth, fever or a tender lump. Treatment may include antibiotics and ultrasound-guided drainage. Persistent inflammation outside breastfeeding must be reassessed because cancer can occasionally mimic infection.

Galactorrhoea

Galactorrhoea is milky discharge unrelated to recent childbirth or breastfeeding. It is usually bilateral and comes from several ducts. Causes include raised prolactin, thyroid disease and medicines such as some antipsychotics, antidepressants, anti-nausea medicines, opioids and hormone treatments.

Headache or visual disturbance with galactorrhoea can suggest a pituitary problem and needs prompt medical evaluation.

Breast cancer or DCIS

Ductal carcinoma in situ (DCIS) and invasive breast cancer can cause nipple discharge, particularly spontaneous unilateral clear or bloody discharge. Concern is greater with a lump, skin dimpling, a newly inverted nipple, nipple ulceration or an armpit lump.

Paget’s disease of the nipple

Paget’s disease can cause persistent one-sided crusting, scaling, bleeding, erosion or discharge from the nipple surface. It can resemble eczema but typically begins on the nipple and may spread to the areola. Persistent nipple “eczema” needs breast assessment and possibly a skin biopsy.

What does the colour mean?

  • Milky: pregnancy, breastfeeding or galactorrhoea
  • Green, brown, black or thick: commonly duct ectasia
  • Yellow or pus-like: infection or inflammation
  • Clear or watery: may occur with papilloma, duct change or cancer and should not be ignored when spontaneous and one-sided
  • Bloodstained: papilloma, duct ectasia, trauma or cancer; it requires assessment

No colour is diagnostic by itself, and apparently harmless-looking discharge can still need assessment if it is spontaneous and unilateral.

When should you see a doctor?

Arrange a breast assessment for any unexplained nipple discharge, particularly if it is spontaneous, persistent, one-sided, single-duct, clear or bloody.

Seek prompt review if discharge occurs with:

  • A new breast or armpit lump
  • Skin dimpling, ulceration or orange-peel change
  • A newly inverted or distorted nipple
  • Persistent nipple rash, crusting or bleeding
  • Redness, swelling, fever or severe pain
  • A personal history of breast cancer

How is nipple discharge assessed?

The clinician asks whether the discharge is spontaneous or expressed, its colour, whether it is unilateral or bilateral, and whether one or several ducts are involved. Pregnancy, breastfeeding, periods, medicines, previous breast disease and family history are reviewed. Both breasts, nipples and regional lymph nodes are examined.

Imaging

Physiological discharge with a normal examination may not require imaging. Pathological discharge is investigated according to age and findings:

  • Targeted breast ultrasound is commonly used, especially in younger patients
  • Diagnostic mammography or tomosynthesis is usually appropriate from about age 30–40 and is routinely considered at 40 and above
  • MRI may be considered in selected patients when conventional assessment is negative but concerning discharge persists

Ductography is now used less often in many centres. MRI is not the first test for every patient.

Biopsy

If imaging reveals a papilloma, mass or suspicious area, an image-guided core or vacuum-assisted biopsy may be performed under local anaesthetic. A nipple-skin biopsy is used when Paget’s disease is suspected.

Testing the fluid alone has limited sensitivity and cannot reliably exclude cancer. A “negative” discharge cytology result should not replace clinical and imaging assessment.

Blood tests

For bilateral milky discharge outside pregnancy or breastfeeding, tests may include a pregnancy test, prolactin level and thyroid function. Medicines and supplements are reviewed. A persistently raised prolactin may require endocrine assessment and pituitary imaging.

Treatment

Treatment depends on the cause:

  • Physiological expressed discharge: reassurance and avoiding repeated nipple squeezing
  • Pregnancy or lactation: breastfeeding support and treatment of trauma or infection when present
  • Galactorrhoea: treatment of thyroid or prolactin disorder and careful medication review
  • Mastitis or abscess: antibiotics when indicated and drainage of an abscess
  • Duct ectasia: symptom control, smoking cessation, infection treatment and sometimes duct surgery
  • Papilloma: observation, vacuum-assisted removal or surgery according to biopsy findings, symptoms and risk
  • DCIS or cancer: treatment according to cancer type and stage

Microdochectomy and major duct excision

A microdochectomy removes the single affected duct. A major duct excision removes a group of ducts beneath the nipple. Surgery may be considered for persistent troublesome discharge, a confirmed duct lesion, concerning findings or when diagnosis remains uncertain despite imaging and biopsy.

Possible complications include bruising, infection, altered nipple sensation, nipple shape change, scarring and inability to breastfeed from the treated breast after removal of major ducts. The need for surgery should be individualised rather than based on discharge colour alone.

Discharge during pregnancy

Physiological discharge is common, and even blood staining can sometimes be benign during pregnancy. Nevertheless, persistent bloody discharge, a mass or unilateral abnormality should be examined. Ultrasound is safe during pregnancy, and biopsy can be performed when necessary. Do not postpone assessment until after delivery if concerning features are present.

Nipple discharge in men

Nipple discharge in a man is uncommon and should be assessed promptly, especially if spontaneous, bloody or associated with a lump or nipple retraction. The same principles of clinical examination, imaging and biopsy apply.

What not to do

  • Do not repeatedly squeeze the nipple to check for fluid
  • Do not insert anything into a duct opening
  • Do not apply unprescribed steroid or antibiotic creams for persistent nipple changes
  • Do not stop prescribed medicine suddenly because it may cause discharge; ask the prescribing clinician
  • Do not assume that all bloody discharge is cancer—or that non-bloody discharge is always harmless

Common questions

Is nipple discharge always cancer?

No. Most nipple discharge has a benign cause. Cancer is more likely when the discharge is spontaneous, unilateral, single-duct, clear or bloody, or associated with another suspicious change.

Can a papilloma become cancer?

Most solitary papillomas are benign. Risk varies if biopsy shows atypical cells, multiple papillomas or an associated mass, so treatment is based on the pathology and imaging together.

Can squeezing cause discharge?

Yes. Repeated expression can stimulate and maintain discharge. Stop squeezing, but seek assessment if fluid continues spontaneously or there are warning signs.

Is green discharge dangerous?

Green or brown discharge commonly results from benign duct ectasia, particularly when from several ducts. It still needs review if spontaneous, persistent, one-sided or associated with a lump or nipple change.

Can I continue breastfeeding?

Usually yes, including during treatment for many cases of mastitis. Individual advice is needed for abscess drainage, unusual bleeding, medication use or planned duct surgery.

Key message

Nipple discharge is often benign, but spontaneous one-sided discharge from a single duct—especially clear or bloody—requires proper breast assessment. Diagnosis depends on history, examination and age-appropriate imaging, with biopsy when a lesion is found. Do not repeatedly squeeze the nipple or rely on colour alone.

Nipple discharge assessment in Lahore

Prof. Dr. Zahid Mahmood assesses nipple discharge, coordinates ultrasound, mammography and biopsy when indicated, and discusses medical treatment, papilloma management, microdochectomy or major duct excision according to the confirmed cause.

For an appointment, call 0300 413 0159 or visit professorzahid.com.

This article provides general education and does not replace personal medical assessment. Bloody or spontaneous one-sided discharge, a breast lump, nipple retraction, persistent nipple rash or a red swollen breast requires prompt clinical review.

Medical references

  1. Williams NS, O’Connell PR, McCaskie AW, editors. Bailey & Love’s Short Practice of Surgery. 28th ed. CRC Press; 2023. Chapter 58, “The breast,” pp. 924–926.
  2. NHS. Nipple discharge: causes, assessment and tests.
  3. American College of Radiology. ACR Appropriateness Criteria: Evaluation of Nipple Discharge.
  4. NICE. Suspected cancer: recognition and referral (NG12), breast cancer recommendations.

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