Quick answer: A breast lump during breastfeeding may reflect inflammation, a milk-filled cyst or an abscess, but a new or persistent lump should be assessed rather than assumed to be a blocked duct. A painful, hot breast with fever or feeling unwell needs prompt advice. See assessment of breast lumps NHS mastitis guidance.
Blocked duct
A firm, tender lump in one breast, usually after a missed feed, tight bra, or skipped breast pump session. The skin may be slightly red. No fever.
Continue normal feeding if able, use a cold compress for comfort and seek feeding support. Avoid deep massage, firm pressure and expressing extra milk beyond what is needed. Seek medical advice if symptoms worsen or do not improve. NHS mastitis self-care guidance.
Galactocele
A smooth, mobile, painless cyst filled with milk. Often noticed weeks to months after starting weaning. Diagnosis is by ultrasound. Small galactoceles often resolve. Large or uncomfortable ones can be aspirated under ultrasound guidance — a simple, painless office procedure.
Mastitis
Painful, red, hot, swollen segment of one breast with fever (>38°C), chills and flu-like symptoms. Caused by milk stasis ± bacterial infection.
Treatment: continue breastfeeding (it is safe and helpful), oral antibiotics for 7–10 days, paracetamol/ibuprofen, frequent emptying of the breast. Most improve in 48–72 hours. Always review at 48 hours — if not improving, ultrasound to rule out abscess.
Breast abscess
Untreated or recurrent mastitis may form an abscess — a pocket of pus. Ultrasound is diagnostic. First-line treatment is needle aspiration under ultrasound guidance (often repeated 2–3 times), with antibiotic cover. Surgical drainage is reserved for very large or multi-loculated abscesses.
When to worry
Book a consultation if you have:
- •A lump that persists more than 2 weeks despite emptying the breast
- •A hard, fixed lump
- •Skin dimpling or nipple inversion
- •Blood-stained discharge
- •Family history of breast cancer These features are unusual in lactational lumps and warrant ultrasound — and core-needle biopsy if needed.
Pregnancy-associated breast cancer
Uncommon but important. Any persistent, non-tender lump in a pregnant or breastfeeding woman should be investigated. Ultrasound and core biopsy are safe during pregnancy and lactation.