Overview

Any fluid that leaks from one or both sides of the non-pregnant or non-breastfeeding breast is called a nipple discharge. Nipple discharge is more frequent in people assigned X at birth and is the third most common breast symptom that requires prompt medical care after breast pain and breast lumps. Over 80% of women develop an episode of nipple discharge during their fertile life.⁷

Nipple discharge, at times, can be a complex diagnostic challenge for healthcare providers since it can be completely benign and can be due to various underlying health conditions. Every human breast has 15 to 20 milk ducts. Nipple discharge can originate from one or more of these milk ducts.¹ 

Due to an increase in breast care awareness, an increasing number of women are asking their healthcare providers about nipple discharge. Nipple discharge is a common complaint in an emergency department. Nipple discharge is expected during the last few weeks of pregnancy, after birth and during the breastfeeding period.¹

It is also normal in non-pregnant and non-breastfeeding womxn, especially during reproductive years. Specific manipulation of the breast, sucking and massaging, can stimulate milk ducts to secrete fluid. Stress can also cause nipple discharge. 

All postmenopausal nipple discharge, however, is significant and can be further investigated. Nipple discharge in men is always abnormal and must be examined promptly.¹

A large number of women are investigated for nipple discharge, but there is little reliable evidence on the best way to explore and manage these patients.⁶

Types of nipple discharge

Lactational nipple discharge: Lactational nipple discharge is considered normal milk production. It is expected during pregnancy and lactation and may continue to be expressed after one year of postpartum or after cessation of breastfeeding. When milky discharge occurs in females without recent pregnancy or lactation, it is commonly called galactorrhea. This is because multiple bilateral milk ducts increase the inappropriate release of prolactin. 

Galactorrhea is a milky discharge from both nipples when a woman is not breastfeeding. Galactorrhea can also occur if you are taking sedatives, high doses of oestrogen, or also in women with irregular menstrual cycles.⁸

Physiological nipple discharge: Nipple discharge is usually benign and white, green, or yellow in colour. It involves multiple ducts and is associated with squeezing the nipple. Physiological nipple discharge could be due to hypothyroidism and medication side effects. 

Pathological nipple discharge: Nipple discharge is usually a clear or bloody secretion. This discharge is unilateral, discharge from a single duct and is spontaneous. It is frequently caused by benign lesions or duct ectasia, but an underlying malignancy is observed in some percentage of cases.⁷

Nipple discharge is an alarming concern for many women. Discharge that happens only when the breast is squeezed may not be a cause for concern. 

A lump with discharge will be a primary concern to your doctor. Breastfeeding women can experience a lump under the areola and discharge. This may be caused by lactational mastitis that occurs with pus-filled infections.⁸

Causes of nipple discharge

Physiological causes:

• Pregnancy
• Lactation
• Postpartum galactorrhea may last up to 2 years after delivery
• Fibrocystic changes in the breast
• After spontaneous or instant termination of pregnancy
• Hormonal changes associated with menstrual cycle
• Duct ectasia¹

Pathological causes:

• Infection
•  Breast abscess
• Neoplastic process of the breast
• Pituitary tumour/prolactinoma
• Breast trauma
• Systemic disease/endocrinopathies that increase prolactin level
• Side effects of medications that inhibit dopamine secretion, such as oral contraceptives and opioids, etc.¹

Diagnosis and evaluation

Clinical examination and medical history

• The first step in examining nipple discharge is to rule out whether it is pathological or physiological. A physiological leak is usually clear or milky and bilateral. Pathological nipple discharge is always unilateral, spontaneous, and varied in appearance. Physical examination aims to differentiate between benign and pathological discharge. 
• Physical examination is essential to investigate the colour of the discharge, the number of ducts involved, and the discharge frequency, whether it is due to stimulation or spontaneous.⁷ It can also provide some clues about the underlying health conditions. For example, a black or green discharge may suggest a pathological cause. Abnormal discharge is frequently associated with other abnormalities, such as mass, swelling, redness and retracted nipples.¹
• Patient’s age is also essential, as women more than 40 years old are at higher risk of developing pathological discharge. Postmenopausal women with nipple discharge are rarely benign. 

Images studies

• Imaging: Your doctor may take imaging tests, such as ultrasound, mammography, x-ray and magnetic resonance imaging (IMR), to help them find the cause
• Biopsy: If a physical exam or imaging test shows abnormalities, your doctor may take a sample of your breast tissue for further investigation.
• Hormone blood test: The doctor will take a blood sample to measure thyroid and prolactin levels.
• Ductogram: Your healthcare provider injects a contrast dye into your milk ducts and then investigates your ducts with a mammogram.⁷

Treatment and management

Treatment of nipple discharge depends on the physical and pathological examinations of the breast. A physiological discharge does not require any treatment. It is essential to stop squeezing or pressing the nipple and breast, as this can lead to more fluid being expressed. As in breastfeeding, the breast continues to produce more fluid to replace the fluid that is removed, which continues as long as you are expressing.⁴

Any red flag symptoms identified during physical examinations in the patient’s urgent referral should be made to the breast cancer clinic.³ Nipple discharge that is spontaneous, blood-stained, and unrelated to pregnancy and breastfeeding needs to be examined further.

This investigation will include images of the breast with a monogram or breast ultrasound. There is also a special X-ray called a ductogram.⁵ The procedure consists of injecting a small amount of dye into the discharging duct of the nipple. This outlines the duct and helps identify abnormal growth in the duct lining.⁴

If abnormalities are found during examination, a biopsy can be recommended. Sometimes, areas need to be removed by the surgeon even if the tests are normal because changes in the nipple duct are hard to see on the monogram and ultra-sound.⁴

Nipple discharge that is due to benign non-cancer breast condition may be treated by keeping the nipple clean, among other treatments. Nipple discharge that occurs due to infection may need hospitalisation.⁸

FAQs

When to seek medical attention?

When you see nipple discharge and any of the following:

• It happens regularly, and it’s not just a one-off. 
• It only comes from one breast. 
• Non-breastfeeding women come out without any pressure. 
• You have other symptoms, such as pain and lumps
• You are over 40s

It's probably nothing serious, but there is a slight chance it could be breast cancer.²

Will I need surgery?

Surgery for nipple discharge is sometimes warranted. This usually happens in cases with significant abnormalities, such as blood-stained discharge or breast cancer is suspected. 

Surgery may also be needed to treat annoying discharge that occurs due to duct ectasia.⁴ 

What's the next step?

Once you know the causes of nipple discharge, you can treat it if necessary. Nipple discharge that is caused by hormonal changes, breastfeeding and pregnancy may not need to be treated. Your healthcare provider may treat discharge from other pathological conditions, such as the colour of the discharge or pain and lumps.

Summary

The awareness about nipple discharge is growing in women, but there is little reliable evidence on the best way to investigate and manage these patients. Nipple discharge is usually not a sign of worry, but it is a good idea to get it checked out. It is also important to be aware that not all nipple discharge is benign. Symptoms like the discharge's colour, frequency, and whether the leak is unilateral or bilateral can help a healthcare provider determine a cause. 

The healthcare provider examines the breast area and runs further imaging tests if necessary. Nipple discharge is rarely a sign of breast cancer, but it is a sign of underlying medical conditions. 

In most cases, nipple discharge can happen in women due to hormonal changes or blocked milk ducts. Nipple discharge in men is always abnormal. Nipple discharge is also abnormal in people over 40. Seek further medical advice if you observe any of the above symptoms