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Breast Abscess — A Comprehensive Review

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1. Definition

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2. Classification

A. Lactational (Puerperal)

• Occurs in breastfeeding women, accounting for ~14% of breast abscesses
• Most common in the first 6 weeks postpartum or during weaning
• Entry of bacteria through cracked or abraded nipple skin

B. Non-Lactational (Non-Puerperal)

• More common — accounts for ~86% of all breast abscesses
• Includes:
  • Peripheral abscess: occurs in breast parenchyma, not near the nipple
  • Subareolar (periductal) abscess: centred on the areola/lactiferous ducts, strongly associated with smoking
  • Complicating breast implants or nipple piercing

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3. Epidemiology & Risk Factors

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4. Microbiology

Primary Organisms

• Staphylococcus aureus — most common overall (51.3% in one series); includes MRSA (~8.6–20% of cases; prevalence rising)
• Streptococcus pyogenes

Secondary / Recurrent Abscess Organisms

• Escherichia coli
• Bacteroides spp. (anaerobes)
• Corynebacterium spp. (associated with granulomatous mastitis)
• Coagulase-negative staphylococci (e.g., S. lugdunensis)
• Pseudomonas aeruginosa, Proteus mirabilis
• Mixed aerobic-anaerobic flora — more common in recurrent and subareolar abscesses

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5. Pathophysiology

1. Bacteria enter through a cracked/abraded nipple or areolar skin
2. Infection establishes in parenchymal tissue (interlobular connective tissue or periductal area)
3. Inflammatory response → cellulitis → loculation of pus
4. In non-lactating women with subareolar disease: squamous metaplasia of lactiferous duct epithelium → keratin plugging → duct occlusion → inspissated debris → superinfection → subareolar abscess → possible lactiferous duct fistula (mammillary fistula) to periareolar skin
5. Milk stasis in lactating women promotes bacterial overgrowth

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6. Clinical Features

Symptoms

• Localised breast pain, tenderness, swelling
• Fever and chills
• Malaise, rigors (in severe cases — toxic appearance)

Signs

• Erythema, warmth, induration over the affected area
• Fluctuance — pathognomonic of abscess (may be absent in deep abscesses)
• Tender palpable mass
• Nipple retraction or discharge (in subareolar/periductal disease)
• Peau d'orange or skin thinning (late — impending rupture)
• Leukocytosis

Key clinical point: In its early stages when cellulitis predominates, an abscess may be clinically indistinguishable; a trial of antibiotics may be appropriate, with ultrasound evaluation for equivocal cases. Women with significant breast abscess "can be quite ill and appear toxic."

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7. Investigations

1. Ultrasound (USS) — Investigation of Choice

• Distinguishes cellulitis (diffuse thickened hyperechoic skin/subcutaneous tissue, no cavity) from a true abscess (fluid collection)
• Characterises the abscess: size, unilocular vs. multiloculated, depth, wall thickness
• Guides needle aspiration or catheter drainage
• USS appearance: inhomogeneous, hypoechoic mass (sometimes described as hyperechoic), often with posterior acoustic enhancement
• Essential for documenting sonographic resolution after aspiration

2. Mammography

• Recommended in women >30 years after the acute phase resolves
• Rules out underlying carcinoma (inflammatory breast cancer can mimic abscess)
• Follow-up at 4–6 weeks post-treatment

3. Microbiological Culture

• Pus/aspirate — send for culture and sensitivity (aerobic + anaerobic)
• Guides antibiotic de-escalation/adjustment
• MRSA screening increasingly relevant

4. Biopsy

• Core needle biopsy if an abscess fails to resolve, or if inflammatory carcinoma is suspected
• Patients should NOT undergo prolonged antibiotic treatment without biopsy if erythema persists, to exclude inflammatory carcinoma

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8. Management

A. Antibiotic Therapy

• Infections should respond within 48 hours; failure warrants imaging to exclude undrained collection or carcinoma
• Duration: typically 7–10 days for lactational mastitis/early abscess
• In lactating women: continue breastfeeding from the unaffected breast; continue emptying the affected breast with a pump

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B. Drainage — The Definitive Treatment

True abscesses require drainage — antibiotics alone are insufficient once pus has formed. — Sabiston, p. 2190

1. Ultrasound-Guided Needle Aspiration (First-line)

• Now the standard of care for most breast abscesses
• Advantages over surgical I&D: less scarring, does not interfere with breastfeeding, no general anaesthesia required
• May require repeat aspirations (mean 3.5 aspirations required for complete resolution)
• Aspirate daily or every other day until resolved
• Document sonographic resolution after each aspiration

• Abscess < 3 cm: ultrasound-guided needle aspiration
• Abscess ≥ 3 cm: ultrasound-guided catheter drainage (e.g., pigtail catheter)

2. Surgical Incision and Drainage (I&D) — Reserved for:

• Failure of needle aspiration and antibiotics
• Skin compromise overlying the abscess (threatened rupture)
• Complex multiloculated abscesses
• Recurrent abscesses
• Very deep/large collections (may require general anaesthesia)

3. Subareolar Abscess — Specific Considerations

• Percutaneous aspiration + antibiotics initially
• Recurrent subareolar abscesses → excision of involved lactiferous duct(s) at the nipple base during a quiescent (infection-free) interval
• Excision of the entire subareolar duct complex for repeated infections (with IV antibiotic cover)
• Rarely, nipple and areola excision for patients with persistent recurrence

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C. Lactational-Specific Management

• Continue breastfeeding — do NOT wean; milk stasis worsens the infection
• Nurse from the non-infected breast; regularly empty the infected breast with a pump
• Apply warm compresses to aid drainage
• NSAIDs for pain and anti-inflammatory effect
• Dicloxacillin 250 mg QID or oxacillin 500 mg QID for 7–10 days

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9. Complications

Although a breast abscess is rarely a harbinger of malignancy, it could be the initial manifestation of a metastatic process. Send aspirated pus for cytology if indicated. — Roberts and Hedges', p. 3771

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10. Special Situations

Subareolar Abscess and Lactiferous Duct Fistula

• Strong association with tobacco smoking (squamous metaplasia of duct epithelium → keratin plugging → ductal obstruction)
• May present as a periareolar mass, nipple discharge, or fistula
• Recurrence rate is high with I&D alone
• Definitive treatment: excision of the lactiferous duct + fistula tract — Berek & Novak's, p. 1784–1792; Sabiston, p. 2191–2198

Idiopathic Granulomatous Mastitis (IGM)

• Mimics recurrent breast abscess or carcinoma
• More common in Hispanic, Middle Eastern, and Southeast Asian women
• Biopsy: non-necrotising granulomata (exclude TB, fungal, sarcoidosis)
• Treatment: antibiotics targeting Corynebacterium (doxycycline, clindamycin, azithromycin), systemic steroids, methotrexate; surgery avoided (poor wound healing) — Sabiston, p. 2203

Inflammatory Breast Cancer — Must Exclude

• Presents with breast enlargement, warmth, erythema, oedema, peau d'orange, nipple retraction
• Clinically indistinguishable from infection
• Diagnosis: mammography + skin/breast biopsy
• Must be considered if breast cellulitis or abscess fails to completely resolve with antibiotics — Tintinalli's, p. 3035–3037

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11. Differential Diagnosis

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Summary Algorithm

Breast pain + erythema + swelling
         ↓
    Ultrasound
   /           \
Cellulitis     Abscess confirmed
   ↓                 ↓
Antibiotics    Culture pus + Antibiotics
(cover MRSA   +
if indicated)  USS-guided needle aspiration
               ↓ (if <3 cm)
           Repeat aspiration q24–48h (mean 3.5)
               ↓ (if ≥3 cm or fails aspiration)
           USS-guided catheter drainage
               ↓ (fails or multiloculated/skin compromise)
           Surgical I&D
               ↓
   Follow-up mammogram >30 years (after resolution)
   Subareolar recurrence → Duct excision (quiescent phase)

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Key References (Standard Textbooks)