Breast abscess

Localised collection of inflammatory exudate in the breast tissue.

Risk factors

• Obese
• Smokers
• Maternal age >30 years
• First pregnancy
• Problems with breastfeeding

Pathophysiology

• Complication of mastitis (cellulitis with breast parenchymal inflammation and swelling)
• Mastitis can develop in two ways
  • Lactational infections
    • Something inhibits milk drainage (nipple trauma and oedema, dehydration and inspissation, oversupply, feeding difficulties, rapid weaning, maternal malnutrition)
    • Collections of stagnant milk
    • Organisms infiltrate through nipple and grow in the stagnant milk
  • Chronic subareolar infections associated with duct ectasia (also called periductal mastitis/non-lactational infections)
    • Risk factors
      • Smoking (majority of patients - 89% in one study)
      • Diabetes
    • Pathophysiology
      • An inflammatory condition of the subareolar ducts
      • Likely caused by toxins, microvascular damage by lipid peroxidases, and altered bacterial flora
      • Duct ectasia and squamous metaplasia ensue, causing stasis of ductal secretions
      • Secondary infections and abscess formation
        • Most often mixed infections with anaerobes and skin flora
        • Infections frequently recur, because the underlying duct is diseased
      • Inflammatory changes can eventually lead to retraction or inversion of the nipple, subareolar masses, and chronic fistula to peri-areolar skin

Classification

• Central usually due to periductal mastitis
• Peripheral less common, sometimes associated with underlying disease states or trauma

Microbiology

• Mostly Staph aureus
• Patients with recurrent abscesses have an increased incidence of mixed flora and anaerobic infection
• Culture of breast milk can guide antibiotics if aspirate is not available
• Blood cultures only helpful if there is evidence of systemic sepsis

Differential diagnosis

• Lactating women:
  • Plugged duct
  • Galactocoele - soft cystic mass that won't be tender. Can diagnose based on aspiration of milk.
• All women:
  • Inflammatory breast cancer. Consider this if the infection does not resolve with appropriate treatment (one week antibiotics), or in non-lactating post-menopausal women without any precipitating factors or systemic signs of infection. Skin thickening due to oedema, erythema, peau d'orange appearance.
    • Investigate with imaging and a punch biopsy of affected skin and possibly core biopsy from deeper masses - if this is negative, doesn't exclude the diagnosis though. May need MRI.
  • Idiopathic granulomatous mastitis (IGM)
    • Rare chronic inflammatory breast disease with unclear cause
      • Possibly related to corynebacterium infection
    • Non-caseating granulomas and microabscesses confined to a lobule
    • Painful mass associated with fistulas, abscesses, inflammatory changes
    • No association with smoking
    • Clinical presentation and radiological findings similar to breast cancer
    • Don't excise it - often followed by persistent wound discharge and failure to heal
    • Steroids and immunomodulators have been used, but variable efficacy
    • The condition tends to resolve spontaneously over 6-18 months, so best to treat supportively, especially treating the episodes of infection and abscess formation, through as minimal an intervention as possible

Management

• Approach
  • Antibiotics and frequent emptying of the breast (step up approach)
• Simple advice:
  • Continued milk draining is important - essentially drains the abscess, resulting in reduced duration of symptoms and improved outcome
  • Not a contraindication to breastfeeding on that side
  • Warm soaks are helpful for mastitis
• Antibiotics
  • Flucloxacillin
  • Consider anaerobic organisms if subareolar location, hidradenitis suppuritiva, recurrent abscess - Augmentin DF would be a good option for a non-lactational infection
  • MRSA is possible but uncommon
• Percutaneous drainage
  • Appropriate first-line when skin is viable
  • Repeat every 2-3 days until no collection remains or the fluid aspirated is serous
  • Few abscesses require more than 2-3 drainages
  • Pigtail catheters can be placed if desired, but not normally necessary
  • Technique
    • Can be USS-guided if desired
    • First try with a 21 gauge needle and inject LA + adrenaline
    • If pus is too thick, use a 19 or 17 gauge needle
    • Wash out cavity until clear
    • Irrigate with LA solution
  • Risk factors for failure of aspiration:
    • Abscess >5cm in diameter
    • Unusually large volume of aspirated pus
    • Delay to treatment
• Surgical drainage
  • Indications
    • Compromised overlying skin (ischaemia/pressure necrosis) - see bottom for examples of compromise
    • Skin overlying abscess is very thin and shiny, or if it appears like the abscess is about to burst through the skin
    • Not responsive to percutaneous aspiration
    • Repeated infections requiring excision of subareolar duct complex, and sometimes the entire NAC
  • Technique
    • See separate topic
• Follow-up
  • MMG and USS six weeks post-presentation for all women to exclude IBC

Complications

• Recurrence
• Mammary duct fistula
  • Communication between major subareolar duct and the skin, usually in the periareolar region
  • Can occur after I+D of a central abscess or after spontaneous drainage
  • Seen in smokers, recurrent abscesses
  • Fistulotomy or fistulectomy can be done. Fistulectomy gives a better result - see topic under 'breast operations'.
• Milk fistula
  • Tract between skin and lactiferous duct after surgical intervention
  • Milk drains through skin
  • Mainly occurs with big incisions or large drains
  • Usually resolves spontaneously
  • If persistent, usually resolves with cessation of lactation - wean from that breast and only nurse from other side
• Antibioma
  • When treated with antibiotics but not drained, it can become a sterile collection - firm, painless, smooth swelling
  • Aspirate it, don't excise it

^ischaemic skin

^pressure necrosis

^thinned skin