Paget's disease of the nipple is the most important differential to exclude in any persistent nipple dermatitis — it is DCIS or invasive carcinoma extending along lactiferous ducts to the nipple epidermis, mimicking contact or atopic eczema. Distinguishing features from benign eczema: strictly unilateral (bilateral rash is almost always contact dermatitis); starts at the nipple spreading to the areola (not vice versa); does not respond to topical corticosteroids after 3-4 weeks; may have associated underlying breast lump or bloodstained discharge. Approximately 50% of Paget's cases have concurrent invasive or in situ carcinoma detectable on imaging. The medicolegal principle: any persistent unilateral nipple rash that has not resolved with appropriate topical treatment within 3-4 weeks requires 2WW referral regardless of how benign it appears.

Intraductal papilloma is the most common benign cause of bloodstained nipple discharge — a small vascular benign epithelial tumour in a major lactiferous duct, typically within 2-3 cm of the nipple. Clinical features: spontaneous bloodstained or serosanguineous discharge from a single duct, reproducible on gentle pressure at a specific periareolar trigger point, most common in women aged 35-55. Approximately 5-10% have associated atypical hyperplasia or DCIS. All patients with spontaneous unilateral bloodstained discharge require 2WW referral for triple assessment — the diagnosis cannot be made in primary care.

Prolactin interpretation requires important caveats: a single elevated result can reflect macroprolactinaemia (biologically inactive complex of prolactin + IgG — detected by standard immunoassay but clinically insignificant, affecting approximately 25% of samples with mildly elevated prolactin), stress, or exercise-related transient elevation. Protocol: request in the morning, fasting, patient rested — not immediately after nipple stimulation or strenuous exercise. Mild elevation (400-2000 mU/L): request macroprolactin test before imaging. Prolactin above 3000-5000 mU/L: MRI pituitary (micro- or macroprolactinoma). Above 8000-10000 mU/L: prolactinoma very likely.

Periductal mastitis recurrence is strongly predicted by smoking — cigarette smoke toxins (methylfurans) cause squamous metaplasia of lactiferous duct epithelium, disrupting the mucus-secreting lining and creating a nidus for ductal infection. Multiple studies show: virtually all patients with periductal mastitis are current smokers; recurrence after surgical duct excision is dramatically higher in smokers. The GP should frame smoking cessation as a direct therapeutic intervention: 'Stopping smoking is the single most effective way to prevent this recurring — the chemicals in cigarettes directly damage the milk ducts.'

The 2WW referral for nipple discharge under NICE NG12 requires two criteria: the discharge is unilateral AND spontaneous (soaks clothing) OR bloodstained. Bilateral expressed milky discharge with no other features in a non-pregnant, non-breastfeeding woman does not automatically require 2WW — it requires prolactin testing and investigation for physiological or drug-induced causes. This distinction prevents unnecessary 2WW referrals for physiological galactorrhoea while ensuring that all potentially pathological discharge receives timely specialist assessment.

Cabergoline withdrawal after sustained prolactin normalisation is possible in a proportion of patients with microprolactinoma — the Endocrine Society guidelines suggest that after 2 years of cabergoline treatment with normalised prolactin and MRI confirming no visible tumour (or significant shrinkage), a slow withdrawal trial over 3-6 months can be attempted. Approximately 25-35% of patients remain in remission off cabergoline at 2 years. The risk of recurrence is higher in: macroprolactinomas, patients who required high cabergoline doses, and patients with residual tumour visible on MRI. During withdrawal and after stopping: prolactin monitoring every 3 months x 1 year. If prolactin rises again: restart cabergoline.

The nipple Candida misdiagnosis in breastfeeding is well-documented — a study by Hogan et al. found that Raynaud's phenomenon was the most common cause of breastfeeding-associated burning nipple pain labelled as thrush. Candida accounts for only approximately 10-15% of breastfeeding nipple pain. The diagnostic principle: Candida nipple infection should only be diagnosed with corroborating evidence — visible oral thrush in the infant; positive nipple swab; or burning pain that persists between feeds AND within the breast tissue (ductal spread). Nipple surface pain only occurring during feeding is not Candida.

The breast self-awareness approach has largely replaced formal monthly self-examination as the recommended strategy in UK public health guidance — Breast Cancer Now and NICE now recommend women be familiar with how their breasts look and feel throughout the month (including normal variation with the menstrual cycle) rather than following a rigid monthly protocol. The rationale: rigid monthly examination can cause anxiety and false reassurance (not finding a 'lump' at the exam may lead to dismissing a subtle change noticed at another time). The self-awareness message is: 'Know your normal — report any change to your GP within 1 week.' This is the message GP consultations should reinforce at every breast-related contact.

The unilateral vs bilateral rule in nipple assessment is the single most rapid discriminating principle — unilateral nipple symptoms have a significantly higher probability of structural or malignant pathology and require 2WW referral; bilateral symptoms are far more likely to be physiological, drug-related, or hormonal. This is a simple, rapid screening question that should be the first assessment in any nipple problem: 'Does this affect one breast or both?' — and the answer should direct the consultation immediately.