Breast abscess

Definition

• Organised collection of inflammatory exudate, or pus, in the breast.

Classification

• Lactational and nonlactational abscesses are distinguished, corresponding broadly to postpartum and non-postpartum disease; they are regarded as distinct entities with their own pathogenesis.

Occurrence & epidemiology

Epidemiology

• Breast infections mostly affect women aged 18 to 50, but abscesses also occur in adolescents, neonates and men.
• Lactational mastitis is common, with a prevalence of about 1–10% among lactating women, whereas an abscess is rare, occurring in about 0.4–0.5% of lactating women in most cohort studies.
• Nonlactational abscesses are seen more often towards the end of the reproductive years.

Aetiopathogenesis

Aetiology and pathogenesis

• An abscess is a complication of both lactational and nonlactational mastitis; during lactation, microorganisms can be transmitted from the infant to the nipple and areola when the epithelial barrier is compromised.
• Lactational abscesses are most often caused by Staphylococcus aureus and streptococci, and MRSA is increasingly seen.
• Nonlactational abscesses are mostly subareolar, are associated with smoking, diabetes and ductal changes and are usually caused by mixed flora; chronic or recurrent abscesses often also involve anaerobes.

Clinical features

• Typical are localised pain, tenderness, swelling and erythema of one breast, frequently with fever, fatigue and flu-like symptoms; the axillary lymph nodes may be reactively enlarged.
• Nonlactational abscesses tend to recur, with reported recurrence rates of 25–50%.
• Particularly in nonlactating women, a serious underlying condition such as malignancy or previously undiagnosed diabetes may be present.

Diagnosis

Typical imaging findings

• Clinical finding: The breast is red and tense; right next to the nipple there is a freshly incised wound with an indwelling drain, and the dressing shows a mix of blood, pus and breast milk.
• Ultrasound: The affected area shows an ill-defined hypoechoic zone with internal echoes (debris) and a heterogeneous structure — consistent with a purulent liquefaction within inflamed tissue.

• Ultrasound is the primary imaging modality; the abscess appears as a focal fluid collection that is irregular and hypoechoic, with poorly defined margins and heterogeneous internal echoes.
• Mobile internal debris within the collection helps to distinguish an abscess from an inflammatory phlegmon; scanning with the probe is frequently tender.
• Blood count and CRP can indicate systemic infection or severe inflammation.

Keep learning in the app

Further reading (selection)

1. StatPearls: Breast Abscess (NCBI Bookshelf)
2. A Pictorial Review on Mastitis: Clinical Aspects, Imaging Features and Complications (J Imaging 2026, PubMed Central)

Cross-references