Define Breast Abscess & Mastitis. Describe its management, pathogenesis and complications.

The Concept

A breast abscess is a localised collection of pus in the breast, almost always the end-result of mastitis (inflammation/infection of breast tissue) that has not resolved. Understanding the two settings in which it occurs — lactational and non-lactational — explains the different organisms, sites and management, and the general surgical principle that pus must be drained applies throughout.

Lactational (puerperal) Mastitis & Abscess

This is the common form, occurring in breastfeeding mothers, typically a few weeks postpartum. The mechanism is milk stasis plus a cracked nipple that lets skin bacteria — usually Staphylococcus aureus — enter and infect stagnant milk, which is an ideal culture medium. It presents with a painful, red, hot, swollen, wedge-shaped area and fever. If a fluctuant collection develops, an abscess has formed.

Non-lactational Abscess

This occurs outside lactation and is strongly associated with smoking and duct ectasia/periductal mastitis. It tends to be periareolar (around the nipple) and is more prone to recur and to form a mammary duct fistula. The organisms are often mixed, including anaerobes, so antibiotic choice differs.

Management

Management follows the stage:

• Cellulitis/mastitis (no pus yet) — antibiotics (flucloxacillin for lactational; co-amoxiclav/metronidazole cover for non-lactational anaerobes), analgesia, and — importantly in lactational mastitis — continued breastfeeding or expression to relieve the milk stasis that drives it.
• Established abscess (fluctuant/pus) — antibiotics alone will not cure a collection, so it must be drained. The modern first-line is ultrasound-guided needle aspiration (repeated as needed), reserving incision and drainage for large or multiloculated abscesses.
• A biopsy of the abscess wall is taken in non-lactational or atypical cases to exclude an underlying inflammatory carcinoma.

Pathogenesis of the Lactational Abscess

The sequence in a breastfeeding mother is worth spelling out because it guides prevention. Milk stasis (from poor latch, missed feeds or blocked ducts) provides a stagnant, nutrient-rich medium; a cracked or fissured nipple provides the portal of entry for skin Staphylococcus aureus; the organism multiplies, causing cellulitic mastitis, which — if not relieved by continued drainage of milk and antibiotics — progresses to a walled-off collection of pus, the abscess. Good latch, frequent feeding and nipple care therefore prevent the whole cascade.

WHY Continue Breastfeeding?

A point that surprises students: mothers with lactational mastitis or even an abscess are generally encouraged to continue breastfeeding or expressing from the affected side. This is because the underlying driver is milk stasis — emptying the breast removes the culture medium and helps resolution — and the milk is not harmful to the infant. Stopping abruptly causes engorgement and worsens the problem.

Complications

Untreated or recurrent disease can lead to a chronic abscess, a mammary duct fistula (especially in the non-lactational, smoking-related periductal disease), scarring and distortion of the breast, and — the diagnosis never to miss — a mistaken label of 'abscess' on what is actually an inflammatory carcinoma, which is why non-resolving lesions are always biopsied.

A Note on the Neonatal & Adolescent Breast

Breast infection is overwhelmingly a condition of the lactating adult, but abscesses occasionally occur in neonates (from maternal-hormone-stimulated breast tissue) and adolescents; these are managed conservatively where possible, with careful incision (avoiding the developing breast bud) if drainage is essential. In all age groups the principle is unchanged — antibiotics for cellulitis, drainage for an established collection, and biopsy for anything that does not behave as expected.

A Note on Recurrent & Atypical Infection

Recurrent periareolar infection in a smoker points to periductal mastitis and duct ectasia, and definitive cure often requires total duct excision plus smoking cessation rather than repeated courses of antibiotics. Any breast inflammation that fails to resolve as expected — persistent erythema, an underlying mass, or skin changes — must be imaged and biopsied to exclude inflammatory carcinoma, a cancer that characteristically mimics infection with a red, swollen, peau-d'orange breast. Vigilance for this mimic is the single most important safety point in managing 'breast infection'.

Breastfeeding is generally continued from the affected side.

• Breast abscess = collection of pus, usually following unresolved mastitis; drain the pus.
• Lactational: milk stasis + cracked nipple → Staphylococcus aureus; painful red wedge-shaped area + fever; keep breastfeeding/expressing.
• Non-lactational: smoking + duct ectasia/periductal mastitis; periareolar, mixed/anaerobic organisms, recurs, may form duct fistula.
• Mastitis (no pus) → antibiotics; established abscess → ultrasound-guided aspiration (first-line) or incision and drainage.
• Biopsy the wall / image if atypical or non-resolving — exclude inflammatory carcinoma; stop smoking in non-lactational disease.