Overview

Nipple discharge can be either physiological (normal) or pathological (linked to an underlying condition).

It is considered physiological when the discharge is milk or colostrum (first breast milk) produced during pregnancy or breastfeeding. It can also occur outside of pregnancy, even after breastfeeding has stopped. In these cases, the discharge is typically bilateral (from both sides), multiductal (from many breast ducts), and is often triggered by breast stimulation.

The discharge is considered pathological when it is watery/bloody, spontaneous, unilateral, localised to a milk duct outlet, and when you are over 40 years of age. While most cases of PND (pathologic nipple discharge) are benign, some require further evaluation. Benign cases, such as intraductal papilloma, occur at a rate of 35-65%, and cases of duct ectasia account for 6-59%. Around 5-23% of surgically evaluated cases show predominance of ductal carcinoma in situ (DCIS) and invasive cancer, which are malignant conditions.

Nipple discharge is one of the most common breast symptoms, and it is estimated that 50-80% of women of reproductive age experience it in some form. International studies indicate that 6-8% of all women referred for breast concerns are seen because of nipple discharge. Bloody secretion is seen in approximately 20% of pregnant women during the second or third trimester in connection with breastfeeding and this is generally considered to be benign.¹

Possible causes

The most common cause of pathological bloody secretion is papillomas that arise from the milk duct wall. This type of secretion is usually spontaneous and is due to the blood supply through the papilloma stalk, leading to an increase in vascular pressure, resulting in transudation and secretion. This is usually long-lasting, unilateral, and localised to a specific duct opening. The secretion may be serous or clear/bloody.¹

Ductectasia can be another cause of pathological secretion. It is an irritating condition in the form of an increase in the width of the milk ducts with the accumulation of debris, and is considered a very common age-related change.¹ 

“Rusty pipe syndrome” is a condition that needs to be considered in a primiparous woman (a person who has given birth once or given birth to a child for the first time) who may present with bloody nipple discharge from both breasts in her early pregnancy days. The very name of the syndrome is due to the colour of the breast milk, which appears pink, orange, brown, or rust-colored, similar to dirty water coming out of an old rusty pipe. A small amount of blood gets mixed with colostrum, or the first breast milk, which leads to the rusty colour of the milk during the first few days of breastfeeding. While in most cases, the condition is spontaneously resolved within 3 to 7 days after the onset of lactation, in some cases, this condition will persist for the first few weeks of lactation and will eventually resolve. Bloody nipple discharge can also occur due to many factors, such as mastitis (inflammation of the breast), cracked nipples, and trauma.²

Papillomas and cancer

An intraductal papilloma is a small, benign growth that forms inside the breast ducts, often near the nipple. It looks a bit like a tiny wart, and may cause nipple discharge, sometimes bloody.³ Intraductal (within the breast duct) papillomas can develop in women irrespective of age. Most commonly, it affects women between the ages of 35 and 55. These growths are rare in men. Intraductal papillomas account for less than 10% of benign breast conditions and under 1% of malignant breast tumours. It is classified as a high-risk precursor lesion due to its association with atypia, ductal carcinoma in situ (DCIS), or even invasive breast cancer.⁴

Predisposing factors⁴

• Family history
• Contraceptive use
• Hormone replacement therapy
• Lifetime oestrogen exposure

Symptoms

An intraductal papilloma may cause spontaneous nipple discharge, which may be bloody or clear. In some cases, the papilloma can be felt as a small lump near the nipple, but this is not always the case. However, most patients with intraductal papillomas do not show any symptoms, especially if the growth is small. Even when symptoms are absent, diagnosing an intraductal papilloma is very important because, in some cases, it may contain hidden (occult) cancer cells or be associated with early stage breast cancer.² 

Evaluation

PND is a clinical diagnosis that requires a thorough assessment. 

• Mammography should be the initial study if you are 40 years of age or older, and men 25 years of age or older
• Ultrasound (US) should be the initial study if you are pregnant, under 40, or a man under 25
• Image-guided biopsy should be performed for any abnormal imaging findings
• Ductoscopy can be useful if initial imaging studies are negative, although it is not widely available
• MRI can be considered as part of the initial work-up if you qualify based on your risk of breast cancer and family history⁵

Treatment and management

• Complete stoppage of the causative drug
• Surgical excision (Lumpectomy) and complete removal of the tumour are recommended

Complications

The tumour itself usually does not cause complications while it is present. But complications may arise after biopsy or surgical excision with a possible cosmetic deformity to the breast, along with pain, bleeding, infection, and fat necrosis (the death of fat tissue, which can cause lumps or firmness in the breast).⁴

Outcomes

The treatment outcomes are excellent for women who undergo surgical removal of the intraductal papilloma. Women should be encouraged to undergo screening mammograms for evaluation of breast conditions. The American College of Radiology and the Society of Breast Imaging recommend annual screening mammograms beginning at age 40 for women of average risk.⁴

FAQs

When to see your doctor?

 When the discharge is pink or bloody in colour, taking place from one breast only without any stimulation, accompanied by redness, lump, or breast pain, especially if you are a woman above 40 years or a man above 25 years. 

What is ductoscopy?

Ductoscopy is a minimally invasive micro-endoscopic technique that makes real-time visualisation of the milk ducts of the breast possible. The procedure can be performed under local anaesthesia at the outpatient clinic and is currently used as a diagnostic tool in the workup of women suffering from PND without suspicious radiologic findings.⁶

Summary

In around 10-20 % of women with bloody nipple discharge, an underlying malignant or pre-malignant condition may be found. The risk increases with age. However, not all nipple discharge is cause for concern. For many women, it is normal to notice a few drops of thick, grey, green, or black viscous fluid when the nipple is squeezed. This is usually benign. If the discharge is purulent (pus-like) and occurs with warmth, redness, and swelling, it could be a sign of mastitis.² In cases where the history, clinical examination, and imaging indicate that the condition is benign, further treatment is not typically necessary. In cases where the secretion is watery/bloody, possibly unilateral, duct excision (removal of the affected milk duct) may be recommended. This serves both to confirm the diagnosis and to treat the cause, even if the clinical mammography appears normal.⁵ 

If you notice any unusual nipple discharge, do not hesitate to speak with your healthcare provider. Early evaluation can give you peace of mind and ensure the right care if needed.