Description

• Breast abscess: localized accumulation of infected fluid within the breast parenchyma
• Mastitis: breast inflammation with or without infection. This can be associated with lactation (puerperal) or nonlactational.
• Associated with lactation or fistulous tracts secondary to squamous epithelial neoplasm or duct occlusion
• System(s) affected: skin/exocrine, immune
• Synonym(s): mammary abscess; peripheral breast abscess; subareolar abscess; puerperal abscess

Pregnancy Considerations
Most commonly associated with postpartum lactation

Epidemiology

• Most common benign breast problem during pregnancy and puerperal period (1)
• Predominantly reproductive age and perimenopausal (between ages 18 and 50)
  • Puerperal abscess: lactational
  • Subareolar abscess: reproductive age through postmenopause (2)
    • 90% of nonlactational breast abscesses are subareolar (1).
    • Nipple piercing associated in increased risk of subareolar abscess (3)
    • Smoking linked to recurrences (3)
• Predominant sex: female
• Higher incidence in African American, diabetic, smoking, or obese women (3)

Incidence

• Ranges estimate up to 11% of breastfeeding women; the Academy of Breastfeeding Medicine cites 3% (2),(4).
• Puerperal abscess has highest incidence within 12 weeks postpartum (3) and while weaning from breastfeeding (4).

Prevalence
Transient condition; recurrences are most strongly associated with smoking, surgical treatment, and increased age (3).

Etiology and Pathophysiology

• Puerperal abscesses:
  • Likely that bacteria (often from infants oral flora) gain entry through cracks/fissures in the nipple (1)
  • Insufficient treatment of mastitis
  • Unattended postpartum engorgement and other situations leading to breast milk stasis (4)
  • Lactose-rich milk and plugged lactiferous duct causing stasis, leading to microbial growth and subsequent abscess formation
• Subareolar abscess:
  • Associated with squamous metaplasia of the lactiferous duct epithelium, keratin plugs, ductal ectasia, fistula formation (2)
  • Higher incidence in patients with nipple piercings (3)
• Microbiology
  • Staphylococcus aureus is most common cause for lactational abscesses (3),(4).
  • Methicillin-resistant S. aureus (MRSA) is a significant cause (4).
  • Less common causes (3)
    • Streptococcus pyogenes, Escherichia coli, Bacteroides, Corynebacterium, Pseudomonas, Proteus
    • Anaerobes and mixed flora are more common in subareolar abscesses.
    • In patients with breast implants, coagulase negative S. aureus is more common.
    • In nonlactational abscesses, lack of growth is a common result.

Genetics
No current evidence to support a genetic predisposition to breast abscess formation (lifestyle/environment have been implicated more often)

Risk Factors

• Maternal age >30 (5)
• Primiparous (5)
• Pregnancy ≥41 weeks’ gestation (5)
• Puerperal mastitis
  • Up to 11% progression to abscess (3)
  • Most often due to inadequate antibiotic and anti-inflammatory treatment of mastitis (4)
  • Risk factors (stasis) (4):
    • Infrequent or missed feeds
    • Poor latch, weak or uncoordinated suckling
    • Damage or irritation of the nipple
    • Nipple inversion or retraction
    • Inefficient removal of milk (by baby or pump)
    • Oversupply of milk
    • Illness in mother or baby
    • Rapid weaning
    • Plugged duct
    • Pressure on the breast (i.e., tight bra, car seatbelt)
    • Maternal stress and fatigue
• General risk factors (3)
  • Smoking; diabetes; obesity
  • African American
  • Nipple piercing
• Medically related risk factors
  • Steroids
  • Breast implants
  • Lumpectomy with radiation
  • Inadequate antibiotics to treat mastitis
  • Topical antifungal medication used for mastitis

General Prevention

• Frequent breast emptying with on-demand feeding and/or pumping to prevent mastitis
• Early treatment of mastitis with milk expression, antibiotics, and compresses
• Smoking cessation to minimize occurrence/recurrence

Commonly Associated Conditions

Lactation, mastitis, weaning