Breast abscess

A breast abscess is a relatively rare but significant complication of mastitis that may occur during breastfeeding, particularly in primiparous women. The clinical context is a key to diagnosis as imaging appearances (particularly ultrasound) can mimic many other entities such as breast carcinoma. 

Epidemiology

Breast abscesses are thought to develop in 5-11% of lactating women with infectious mastitis ³. In this context they are also referred to as lactational abscesses. Note, that a neonatal breast abscess is a different entity occurring on a background of neonatal mastitis.

Clinical presentation

There is often an antecedent clinical history of mastitis. The breast usually appears hot, red, and indurated. The course may be affected by antibiotic therapy depending on when the patient is imaged.

Pathology

A breast abscess is defined as an inflammatory mass that drains purulent material either spontaneously or on incision. The predominant infectious organism is Staphylococcus aureus, often the penicillinase-producing and methicillin-resistant S. aureus ¹². Other causative organisms include Staphylococcus epidermidis and Proteus mirabilis.

Peripheral breast abscesses have generally been associated with mastitis during breastfeeding, but previous reports indicate that abscesses are common among non-lactating women.

Associations

• increased incidence in those with diabetes

Classification

For clinical relevance and for planning treatment breast abscesses are classified as:

• puerperal abscesses: seen in primiparous mothers
• non-puerperal central abscesses: commonest non-breastfeeding abscess, seen mostly in young women; especially smokers
• non-puerperal peripheral  abscesses: less commonly seen. Seen in older women with underlying chronic medical conditions like diabetes, rheumatoid arthritis; women taking steroids; or following recent breast intervention

Radiographic features

The clinical context is crucial to image interpretation.

Breast ultrasound

Ultrasound is considered the most useful initial imaging modality when a breast abscess is suspected. It is also the imaging method of choice to monitor progress, response to therapy and to ensure resolution. For the purpose of follow up the three dimensional measurement of the abscess and the volume of the contents should be given.

Sonographic features suggestive of a breast abscess include:

• hypoechoic collection, mostly multiloculated
• no vascularity within the collection
• posterior acoustic enhancement due to fluid content
• an echogenic, vascular rim

Mammography

Mammography is very rarely indicated or useful. Mammography is recommended to exclude the possibility of malignancy in non-puerperal abscesses, in ladies over 30 years and in puerperal abscesses with a prolonged clinical course. Mammographic appearances are often non specific and in the age group where breast abscesses are most often found, mammography is rarely done.

Findings which may be demonstrated are:

• skin thickening
• asymmetric density, mass or distortion

These findings are not specific for abscess or malignancy; however presence of suspicious microcalcifications is more specific for malignancy and a biopsy to rule out carcinoma should be carried out.

Treatment and prognosis

Antibiotic treatment combined with ultrasound-guided aspiration is the treatment of choice. Repeated aspiration may be required but is recommended over placement of percutaneous catheter due to the risk of cutaneous fistula and patient discomfort. In rare cases surgical incision and drainage may be required.

It is recommended that breastfeeding continue throughout treatment to prevent milk stasis ¹³. 

Differential diagnosis

On ultrasound a breast abscess can easily mimic other entities such as a breast malignancy or a breast hematoma on imaging grounds alone. In practice, the most difficult differentiation is from a galactocele.