Breast abscess

A breast abscess is a relatively rare but significant complication of mastitis that may occur during breast-feeding, 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.  Rubor, calor, dolor, functio lysa.

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.

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 spontaneous or on incision. The predominant infectious organism is Staphylococcus aureus, and often is the penicillinase-producing type. Other common types include Staphylococcus epidermidis and Proteus mirabilis.

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

Assocations

• increased incidence in those with diabetes

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.

Aspiration of a breast abcess is easily and quickly performed under ultrasound guidance and the patients are immensely grateful for the symptomatic relief. These are some of the most grateful patients in medicine.

The ultrasound appearance of an abcess in the breast  is protean but may be typically seen as a irregular hypo-echoic breast lesion with varying degrees of definition. Sonographic that suggestive of a breast abscess include 

• adjacent interstitial fluid ⁹
• presence of a hypo-echoic rim ⁹

Mammography

Mammography is vary rarely indicated or useful. Mammographic appearances are often non specific and in the age group where breast abscesses are most often found, mammography is rarely done. It adds radiation but not information in this group of patients. Where resolution is incomplete or there are clinical concerns about the diagnosis, mammography may be  indicated on a case to case basis.

Treatment and prognosis

Mastitis and some abscesses may respond to antibiotic treatment with aspiration if needed. Unfortunately, even with adequate treatment, a significant proportion of breast abscesses recur, especially the non-puerperal abscesses ¹⁰.

Breast feeding from the affected breast should  cease until resolution is complete.

Differential diagnosis

On ultrasound a breast abscess can easily mimic other entities such as a breast malignancy or a breast haematoma on imaging grounds alone. In practice, the most difficult differentiation is from a  galactocoel. The lesions occur in the same cohort and the  imaging characteristics are very similar to a galactocoel. Clinical differentiation is key. Be very weary of lesions that enlarge or lesions that look like an abcess but are not painful or warm to the touch. Carcinomas can be estrogen receptive and can grow very significantly in pregnancy. Not all lesions found in pregnancy and lactation can simply be assumed to be an abcess or galactocoel. Tread wearily with lesions that do not resolve or that  linger. Close follow up is indicated.