What causes nipple discharge?

Causes of Nipple Discharge

Nipple discharge is most commonly caused by benign conditions, with intraductal papilloma (35-48%) and ductal ectasia (17-36%) being the most frequent causes, while malignancy accounts for only 3-29% of pathologic cases. 1

Classification of Nipple Discharge

Nipple discharge can be categorized as either physiologic or pathologic:

Physiologic Discharge

• Characteristics:

  • Often provoked rather than spontaneous
  • Comes from multiple duct orifices
  • Typically bilateral
  • White, green, or yellow in color
  • Not associated with malignancy 2, 1
  • May be milky in appearance 2

• Common causes:

  • Hyperprolactinemia due to:
    • Medications (particularly antipsychotics)
    • Pituitary tumors
    • Endocrine disorders 3

Pathologic Discharge

• Characteristics:

  • Spontaneous (occurs without breast manipulation)
  • Comes from a single duct orifice
  • Usually unilateral
  • Serous or bloodstained 1
  • Requires further evaluation

• Common causes and their frequency:

  1. Intraductal papilloma/papillomatosis: 35-48% of cases
  2. Ductal ectasia: 17-36% of cases
  3. Malignancy: 3-29% of cases (with larger studies estimating 11-16%) 1
  4. Breast abscesses/infections 4

Special Considerations

Age-Related Risk

• Risk of malignancy increases with age 1
• Women under 30 years have a very low cancer risk (0.4% or lower) 1
• Women 40 years and older have a higher risk (1 in 69) 1

Male Nipple Discharge

• Requires immediate evaluation due to a significantly higher malignancy risk (23-57%) 1
• Should never be dismissed as benign without proper investigation 1

Clinical Significance

• Nipple discharge is the third most common breast complaint after breast pain and breast masses 5
• It accounts for 2-5% of medical visits by women 6
• It is the presenting symptom in 5-12% of breast cancers 6
• Up to 50% of women in their reproductive years can express one or more drops of fluid from the breast 5

Diagnostic Approach

For pathologic nipple discharge, the following diagnostic approach is recommended:

1. For patients ≥30 years: Diagnostic mammography with possible digital breast tomosynthesis AND ultrasound 1
2. For patients <30 years: Ultrasound as initial imaging, followed by mammography if indicated 1
3. If initial imaging is negative but symptoms persist: Consider MRI of the breast or ductography/galactography 1

Clinical Pearls and Pitfalls

• Key Pitfall: Dismissing male nipple discharge, which carries a high malignancy risk (up to 57%) 1
• Important Consideration: Delays in diagnosis are associated with higher rates of node-positive disease, highlighting the importance of timely evaluation 1
• Clinical Pearl: When both mammogram and subareolar ultrasound are negative in patients with pathologic nipple discharge, the risk of carcinoma approaches zero 2
• Reassurance Point: Most nipple discharges result from clinically insignificant benign processes 5