Breast Abscess

Breast abscess is a localised collection of pus within the breast tissue, most often complicating lactational mastitis (about 3 to 11 percent of mastitis cases develop abscess), but also seen in non-lactational disease (periductal mastitis, smoking, diabetes, nipple piercing, immunosuppression).

• Organisms:
  • Lactational: Staphylococcus aureus (including MRSA), streptococci.
  • Non-lactational: S. aureus, anaerobes (Bacteroides, Peptostreptococcus), enterococci, Corynebacterium, coagulase negative staphylococci, mixed flora.
  • Granulomatous mastitis and tuberculous abscess are less common mimics.
• Risk factors: nipple trauma, delayed or inadequate treatment of mastitis, first time mothers, age over 30, caesarean section, infant tongue tie, smoking, diabetes, obesity, nipple piercing, breast implants, previous breast surgery or abscess.
• Complications: sepsis, mammary fistula, recurrence, scarring and breast deformity, premature cessation of breastfeeding, delayed diagnosis of underlying malignancy (inflammatory breast cancer can mimic abscess).

• A painful, firm or fluctuant lump, localised warmth, redness or violaceous skin, tender swelling, fever, malaise, tachycardia; shiny, thinned skin overlying may point to imminent rupture; sometimes purulent discharge from the nipple or skin sinus.
• Axillary lymph nodes tender.
• Often follows an episode of mastitis that has not settled within 48 hours of treatment.
• Red flags: sepsis (hypotension, tachycardia, confusion), spreading cellulitis, necrotic skin, rapid enlargement, poorly responsive to antibiotics, recurrent abscess, non-lactating woman with a lump, bloody discharge, peau d'orange, nipple retraction, mass persisting after drainage (exclude malignancy).

• Clinical examination, confirmed with breast ultrasound (hypoechoic or complex collection with debris and posterior enhancement; also guides aspiration).
• Culture of aspirated pus (aerobic and anaerobic) and sensitivity testing, with MRSA screen where relevant.
• Bloods: full blood count, CRP, blood cultures if systemic upset, glucose or HbA1c for recurrent infection.
• Mammography with biopsy of the wall for non-lactating women, women over 35, or if an underlying mass is suspected or the abscess fails to resolve.
• Differential: mastitis without abscess, galactocele, inflammatory breast cancer, fat necrosis, granulomatous mastitis, haematoma, infected cyst.

• Drainage plus antibiotics is the treatment. Ultrasound guided needle aspiration under local anaesthetic (lidocaine 1 percent) is the preferred first step for abscesses up to about 3 to 5 cm: aspirate using a wide bore needle (16 to 18 gauge), repeated every 1 to 3 days until no pus returns, with ultrasound guidance; send fluid for culture; success in about 80 to 90 percent.
• Incision and drainage (small incision with a drain or packing) for large abscesses, multiloculated collections, thinned or necrotic skin, failed aspiration; place incisions in radial direction or along skin creases for cosmesis; refer to a breast surgeon.
• Antibiotics (start empirically and adjust by culture; 7 to 14 days depending on response):
  • Lactational: flucloxacillin 500 mg to 1 g orally four times daily for 7 to 10 days.
  • Non-lactational (anaerobes likely): co-amoxiclav 625 mg orally three times daily for 7 to 10 days; or flucloxacillin 500 mg four times daily plus metronidazole 400 mg three times daily.
  • Penicillin allergy: clindamycin 300 to 450 mg orally four times daily; or doxycycline 100 mg orally twice daily with metronidazole 400 mg three times daily for non-lactational abscess.
  • MRSA: trimethoprim-sulfamethoxazole 160/800 mg orally twice daily or doxycycline 100 mg twice daily or clindamycin chosen by sensitivities; intravenous vancomycin 15 to 20 mg/kg every 8 to 12 hours with monitoring of levels for severe infection.
  • Sepsis or severe cellulitis: admit; intravenous flucloxacillin 1 to 2 g every 6 hours or co-amoxiclav 1.2 g every 8 hours or vancomycin as indicated; fluid resuscitation.
• Continue breastfeeding from the affected breast if the infant can latch without contact with the wound or drain; otherwise express milk by hand or pump from the affected side to maintain supply and discard milk only if frank pus is mixed. Most antibiotics listed are compatible with breastfeeding; avoid tetracyclines beyond short courses in the infant's first weeks.
• Analgesia: paracetamol 1 g every 6 hours; ibuprofen 400 mg three times daily with food; opioid only briefly if severe.
• Non-lactational abscess: stop smoking, optimise diabetes control, treat periductal inflammation; recurrent abscess needs excision of the involved duct system (specialist); biopsy to exclude carcinoma.
• Follow up in 2 to 3 days for the wound and repeat ultrasound, until resolution; failure to resolve within 2 weeks, or a residual mass, needs imaging and biopsy.
• Return advice: spreading redness, rigors, new lump, fever, wound discharge, or reduced feeding of the infant.