Define Nipple Discharge. Describe its causes and investigations.

The Concept — the Key Questions

Nipple discharge is common and usually benign, but it can occasionally signal cancer, so the assessment is a structured attempt to answer a few key questions: is it from one duct or many, one breast or both, spontaneous or only on squeezing, and what colour is it? The answers separate the reassuring physiological discharge from the discharge that needs investigation. Broadly, bilateral, multi-duct, non-spontaneous discharge is benign; unilateral, single-duct, spontaneous or blood-stained discharge is 'suspicious' and must be worked up.

Physiological & Galactorrhoea

Physiological discharge — small amounts of milky or greenish fluid from multiple ducts of both breasts, only on squeezing — is benign and needs only reassurance. Galactorrhoea is a copious milky discharge unrelated to lactation, caused by hyperprolactinaemia — from a pituitary prolactinoma, drugs (dopamine antagonists), or hypothyroidism — so it is investigated with a serum prolactin, thyroid function and, if raised, pituitary imaging.

Pathological Causes BY Colour

• Blood-stained (or serosanguinous) — the most important to investigate. The commonest cause is a benign duct papilloma, but it can also be duct ectasia or an underlying carcinoma (especially DCIS).
• Thick, cheesy, green/brown, multi-duct — typical of duct ectasia in an older woman.
• Purulent — suggests infection (abscess/periductal mastitis).
• Milky — physiological or galactorrhoea (see above).

Assessment & Management

A patient with suspicious (single-duct, spontaneous or bloody) discharge undergoes triple assessment — examination (looking for a lump and identifying the discharging duct), imaging (mammography ± ultrasound), and testing the discharge (for blood) with biopsy of any mass. Where no cause is found but the discharge is troublesome or suspicious, the discharging duct(s) are excised — microdochectomy (single duct, to preserve breastfeeding in the young) or total duct excision (Hadfield's procedure) (multiple ducts in the older woman) — which is both diagnostic and therapeutic.

The Duct Papilloma

Since it is the commonest cause of the most worrying discharge, the intraductal papilloma deserves emphasis. It is a small, benign, wart-like epithelial growth within a large subareolar duct, and as it is friable it bleeds, producing spontaneous, unilateral, single-duct, blood-stained discharge — often with no palpable lump. It is diagnosed and treated by microdochectomy (excising the affected duct), which also provides histology to confirm it is benign and exclude a papillary carcinoma.

A Structured Approach

Faced with nipple discharge, a logical scheme is: first decide if it is galactorrhoea (bilateral, milky, multi-duct → check prolactin/thyroid and drugs); if not, decide whether it is benign-type (bilateral, multi-duct, on pressure, green/brown → reassure ± treat duct ectasia) or suspicious-type (unilateral, single-duct, spontaneous, bloody → full triple assessment and duct excision). This algorithm ensures the small number of sinister discharges are always investigated while the majority are reassured.

Investigations

Useful investigations include examination to identify the discharging duct and any lump, testing the fluid for blood, mammography and ultrasound (and, for a single discharging duct, sometimes ductography or ductoscopy), and cytology of the fluid (though a negative cytology does not exclude cancer). A discrete lesion is biopsied.

A Note on Malignant Causes

Although most nipple discharge is benign, the features that raise concern for an underlying malignancy (usually DCIS, occasionally invasive or papillary carcinoma) are a bloody or serous single-duct discharge in an older woman, an associated mass, or associated microcalcification on mammography. This is why the 'suspicious' discharge is never simply reassured: even though the commonest cause (duct papilloma) is benign, only triple assessment and, where indicated, duct excision can safely exclude cancer.

A Structured Diagnostic Algorithm

Faced with nipple discharge, a stepwise scheme keeps the assessment safe: first identify galactorrhoea (bilateral, milky, multi-duct → check prolactin, thyroid function, drug history); then separate clearly benign-type discharge (bilateral, multi-duct, on expression, green/brown → reassure, treat duct ectasia) from suspicious discharge (unilateral, single-duct, spontaneous, blood-stained → full triple assessment and, where needed, duct excision). This algorithm reliably investigates the small proportion of sinister discharges while reassuring the majority, and it always ends by excluding an underlying carcinoma before a benign cause is accepted.

Blood-stained single-duct discharge requires investigation.

• Key questions: single vs multiple ducts, unilateral vs bilateral, spontaneous vs on squeezing, and colour.
• Benign/physiological: bilateral, multi-duct, on squeezing, milky/green — reassure.
• Galactorrhoea (milky, non-lactational) = hyperprolactinaemia (prolactinoma, drugs, hypothyroidism) → prolactin, TFTs, pituitary imaging.
• Suspicious: unilateral, single-duct, spontaneous, blood-stained → triple assessment; commonest cause of bloody discharge is duct papilloma (but exclude carcinoma/DCIS).
• Treat by microdochectomy (single duct) or total duct excision/Hadfield's (multiple ducts) when needed.