AKT · Endocrine/Breast

Mastitis & breast abscess

Breast infection/inflammation (lactational — Staph aureus; also periductal in smokers)

Overview

Inflammation/infection of the breast — most commonly LACTATIONAL (milk stasis → Staph aureus), also non-lactational periductal mastitis (smokers). Presents with a red, hot, tender, swollen segment ± systemic upset; if it forms a fluctuant collection it is an abscess (needs drainage). The crucial mimic is inflammatory breast cancer.

Recognise

Painful, red, hot, swollen breast segment, often wedge-shaped; fever/malaise; usually in a breastfeeding woman
Milk stasis/cracked nipple (lactational); smoking + periareolar inflammation/nipple inversion (periductal/non-lactational)
Abscess: fluctuant, tender collection (ultrasound confirms)

Red flags

Not settling on antibiotics, or an older non-lactating woman with a red breast → exclude INFLAMMATORY breast cancer (refer)
Abscess (fluctuant) → needs ultrasound-guided aspiration/drainage

Differentials & how to tell them apart

Inflammatory breast cancererythema, peau d'orange, NOT settling on antibiotics, older/non-lactating — must exclude with biopsy

Breast abscessfluctuant collection — needs drainage, not just antibiotics

Engorgement/blocked ductdiffuse fullness without infection — relieved by feeding/expressing

Investigations

Clinical; ultrasound if abscess suspected (aspiration/drainage). Culture milk/pus. Consider biopsy if not resolving (inflammatory cancer).

Management

Effective milk removal + analgesia; flucloxacillin if infective; drain an abscess

1Lactational mastitis: continue feeding/expressing (effective milk removal) + analgesia; add flucloxacillin if not settling, systemically unwell, or culture-positive. Drain an abscess (ultrasound-guided aspiration/I&D).Gate: A breast that does NOT settle on antibiotics (especially in an older, non-lactating woman) must be biopsied to exclude INFLAMMATORY breast cancer; a fluctuant collection is an abscess needing drainage, not more antibiotics
2Recurrent periductal mastitis → smoking cessation; recurrent/complex → surgical referral; rule out inflammatory cancer for non-resolving cases.

Continue breastfeeding/expressing + analgesia — milk drainage is key in lactational mastitis

Flucloxacillin — if infection (not settling with milk removal, systemically unwell, cracked nipple/culture-positive); erythromycin/clarithromycin if penicillin-allergic

Ultrasound-guided aspiration/incision & drainage — for an abscess

Key points

Red, hot, tender breast in a breastfeeding woman = mastitis → milk removal ± flucloxacillin; fluctuant = abscess (drain). The non-negotiable: a red breast that won't settle is inflammatory cancer until biopsy proves otherwise.

Monitor & prognosis

Resolution; re-image/biopsy if not settling.

Good; recurrence with smoking (periductal).

Source: NICE CKS Mastitis and breast abscess