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
• Predominantly reproductive age and perimenopausal (between ages 18 and 50 years)
  • Puerperal abscess: lactational
  • Subareolar abscess: reproductive age through postmenopause:
    • 90% of nonlactational breast abscesses are subareolar.
• Predominant sex: female
• Higher incidence associated with diabetes, smoking, and obesity

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.
  • Mammary dysbiosis is a consequence of multiple factors including genetic, breastfeeding related, medical, and microbial
    • Likely that bacteria (often from infants oral flora) gain entry through cracks/fissures in the nipple
    • Insufficient treatment of mastitis
    • Unattended postpartum engorgement and other situations leading to breast milk stasis
• Subareolar abscess:
  • Associated with squamous metaplasia of the lactiferous duct epithelium, keratin plugs, ductal ectasia, and fistula formation
• Microbiology
  • Staphylococcus aureus is the most common cause for lactational abscesses.
  • Methicillin-resistant S. aureus (MRSA) is a significant cause.
  • Other common causes include coagulase-negative Staphylococcus and Streptococcus species.
  • Less common causes:
    • Escherichia coli, Enterobacteriaceae, Corynebacterium, and Pseudomonas
    • Anaerobes
    • Polymicrobial

Risk Factors

• Smoking, maternal age >30
• Primiparous, pregnancy ≥41 weeks’ gestation
• Diabetes
• Obesity
• 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(s)
  • Pressure on the breast (i.e., tight bra, car seatbelt)
• Medically related risk factors:
  • Steroids (oral or topical)
  • Breast implants
  • Lumpectomy with radiation
  • Inadequate antibiotics to treat mastitis
  • Topical antifungal medication used for nipple pain/infection

General Prevention

• Frequent movement of milk with on-demand feeding and/or pumping to prevent mastitis
• Early treatment of mastitis with movement of milk on a regular basis, reduction in inflammation (with use of ice and/or NSAIDs), pain control (with acetaminophen) and antibiotics (if indicated)
• Smoking cessation to minimize occurrence/recurrence

Commonly Associated Conditions

Lactation, mastitis, weaning

History

• Tender breast lump, usually unilateral
• Breastfeeding, weaning, or returning to work
• Recent or recurrent mastitis
• Systemic malaise (usually less than with mastitis)
• Localized erythema, warmth, edema, pain
• Fever, nausea, vomiting
• Prior breast infection
• Decreased breast milk supply on affected breast
• Spontaneous nipple drainage
• Diabetes
• Smoking
• Perimenopausal/postmenopausal

Physical Exam

• Fever, tachycardia (not always present)
• Erythema or hyperpigmentation of overlying skin
• Palpable mass, sometimes fluctuant
• Tenderness on palpation
• Induration
• Local edema
• Draining pus or skin ulceration
• Nipple and/or skin retraction
• Regional lymphadenopathy
• Puerperal abscesses are generally peripheral; non-lactational abscesses are more commonly found in periareolar/subareolar region.

Differential Diagnosis

• Engorgement
• Plugged milk duct
• Mastitis
• Galactocele (sometimes referred to as a milk lake)
• Fibrocystic breasts
• Fat necrosis
• Tuberculosis (potentially associated with HIV infection)
• Sarcoid
• Granulomatous mastitis
• Syphilis
• Foreign body reactions (e.g., to silicone and paraffin)
• Mammary duct ectasia
• Carcinoma (inflammatory or primary squamous cell)

Diagnostic Tests & Interpretation

General Measures

• Cold and/or warm compresses for pain control (2)[A]
• Continue to move milk (via direct feeding or pumping) to drain the affected breast (2)[A].
• US-guided needle aspiration to drain abscess; without drainage, antibiotics are ineffective (2)[A],(3)[A].

  • Acceptable to start antibiotics while working to get patient to drainage/aspiration

Medication

Issues for Referral

If showing signs of hemodynamic instability, patient should be referred for inpatient stabilization and care (rare).

Additional Therapies

• NSAIDs for analgesia, anti-inflammatory effect, and/or antipyresis (2)[A]
• Rest, adequate fluid intake, good nutrition (2)[A]
• Application of heat to the breast just prior to feeding/milk expression may help with adequate milk flow (2)[A].
• Cold packs applied after a feeding/milk expression can reduce pain and edema (2)[A].

Surgery/Other Procedures

• Current best practice recommendation suggests:
  • Aspiration (using 18- to 21-gauge needle) with or without US guidance for abscesses <3 cm (1)[A],(3)[A] (Serial aspirations may be necessary.)

    • US-guided aspiration of breast abscess is preferred to incision and drainage (I&D) in most cases due to better cosmesis and faster recovery.
  • Consider US-guided percutaneous catheter placement if abscess is >3 cm (3)[A].
  • Consider I&D using a no. 15 blade scalpel if abscess is >5 cm, recurrent, or chronic (3)[A].
• Biopsy nonpuerperal abscesses to rule out malignancy; remove all fistulous tracts in nonlactating patients as well (3)[A].

Complementary & Alternative Medicine

• Lecithin supplementation (to support milk flow as an emulsifying agent)
• Probiotics (to support microbiome)
• Acupuncture (may help with breast engorgement and prevention of breast abscess)
• Breast lymphatic massage (may ease engorgement)
• Judicious use of cabbage leaves applied over affected area (to decrease inflammation and milk production)

Admission, Inpatient, and Nursing Considerations

• Outpatient, unless systemically immunocompromised, septic, or requiring inpatient antibiotic treatment
• Hospital-grade breast pump should be made available to patient from time of admission.

Follow-up Recommendations

Diet

Patient Education

• Wound care, rest, breast milk movement
• Continue with breastfeeding or pumping to prevent engorgement.

Prognosis

• Drained abscess heals from inside out (in 8 to 10 days)
• Subareolar abscesses frequently recur, even after I&D and antibiotics; may require surgical removal of ducts

Complications

• Fistula: mammary duct or milk fistula
• Poor cosmetic outcome
• Early cessation of breastfeeding

Additional Reading

Zhou F, Li Z, Liu L, et al. The effectiveness of needle aspiration versus traditional incision and drainage in the treatment of breast abscess: a meta-analysis. Ann Med. 2023;55(1):2224045. doi:10.1080/07853890.2023.2224045.  [PMID:37350731]

ICD-10

• N61 Inflammatory disorders of breast
• O91.13 Abscess of breast associated with lactation
• O91.12 Abscess of breast associated with the puerperium
• O91.119 Abscess of breast associated with pregnancy, unsp trimester
• O91.112 Abscess of breast associated w pregnancy, second trimester
• O91.113 Abscess of breast associated with pregnancy, third trimester
• O91.111 Abscess of breast associated with pregnancy, first trimester

SNOMED

• 28432003 Abscess of breast (disorder)
• 200374003 Obstetric breast abscess - delivered
• 237438009 subareolar breast abscess (disorder)
• 55704005 abscess of breast, associated with childbirth (disorder)