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 years)
  • Puerperal abscess: lactational
  • Subareolar abscess: reproductive age through postmenopause (2)
    • 90% of nonlactational breast abscesses are subareolar (1).
• Predominant sex: female
• Higher incidence in African American, diabetic, tobacco use, or obese women

Incidence
Ranges between 3% and 11% of women with mastitis (1),(3)

Prevalence
Transient condition usually as a complication of mastitis; mastitis prevalence ranges between 1% and 10% (1).

Etiology and Pathophysiology

• Puerperal abscesses:
  • Associated with hyperlactation and dysbiosis (disrupted milk microbiome); these can lead to ductal narrowing and inflammation and subsequently to reduced milk flow, obstruction, plugged lactiferous duct causing stasis, microbial growth, and infection (3).
  • Mammary dysbiosis is a consequence of multiple factors including genetic, breastfeeding-related, medical, and microbial (3).
  • 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 (3)
• Subareolar abscess:
  • Associated with squamous metaplasia of the lactiferous duct epithelium, keratin plugs, ductal ectasia, and fistula formation (2)
• Microbiology
  • Staphylococcus aureus is the most common cause of lactational abscesses (1),(2).
  • Methicillin-resistant S. aureus (MRSA) is a significant cause (1).
  • Other common causes include coagulase-negative staphylococci and Streptococcus spp. (2),(3).
  • Less common causes (1):
    • Escherichia coli, Enterobacteriaceae, Corynebacterium, and Pseudomonas
    • Anaerobes
    • May be polymicrobial

Genetics
Maternal genetics may play a role as protective and predisposing factors for mammary dysbiosis, which is associated with the pathophysiology (3).

Risk Factors

• Smoking, maternal age >30 years
• Primiparous, pregnancy ≥41 weeks’ gestation
• Diabetes and obesity
• African American
• Nipple piercing
• Milk stasis:
  • 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
• 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