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A breast abscess is a localized collection of pus within the breast tissue, typically resulting from bacterial infection, most commonly in lactating women. It represents a complication of mastitis, but can also occur in non-lactating women, especially in those with smoking history or diabetes.

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Etiology

Risk factors:

Type Description
Lactational (puerperal) Most common; due to milk stasis and bacterial infection during breastfeeding
Non-lactational Associated with periductal mastitis, smoking, diabetes, trauma, or nipple piercing
Infectious agents Staphylococcus aureus (most common), Streptococcus, anaerobes, rarely Mycobacterium or fungi

Clinical Features

Feature Description
Localized breast pain Severe, throbbing; worsens with palpation
Swelling and redness Overlying skin may show erythema, warmth, and induration
Fluctuant mass Suggests localized pus collection
Fever, malaise Systemic signs of infection
Purulent nipple discharge Sometimes present
Axillary lymphadenopathy May be palpable on the same side

Complications

Radiology

Modality Imaging features
US • Complex cystic lesion: Thick-walled, irregular, hypoechoic or mixed echogenic mass
• Internal debris/septations: Suggestive of purulent material
• Peripheral vascularity: Hyperemia around the lesion (on color Doppler)
• Compressibility: Typically non-compressible (unlike galactocele)
• Skin thickening: Overlying the abscess cavity
Mammography Not routine in acute cases; may be done in non-lactating women or to rule out underlying malignancy
• Ill-defined asymmetry, skin thickening, distortion; rarely microcalcifications
• Painful in acute setting; low sensitivity in dense or lactating breasts
MR Rarely used to evaluate extent, chronic abscess, or recurrent infection
• Rim-enhancing fluid collection with adjacent inflammatory changes

![Breast abscess. A 45-year-old woman presented with a palpable area in the right breast. Mediolateral oblique (a) mammogram shows a focal asymmetry in the upper outer breast (arrow) and associated trinagular palpable marker. Power Doppler ultrasound images (b, c) reveal two hypoechoic, oval masses with peripheral vascularity in the same region (asterisks). Axial post-contrast T1-weighted MRI (d), sagittal T2-weighted MRI (e), and postcontrast subtraction T1-weighted MRI (f) show two T2-hyperintense, rim-enhancing masses (arrows). Needle biopsy showed acute inflammatory cells consistent with abscess without evidence of malignancy

Guirguis, M.S., Adrada, B., Santiago, L. et al. Mimickers of breast malignancy: imaging findings, pathologic concordance and clinical management. Insights Imaging 12, 53 (2021). https://doi.org/10.1186/s13244-021-00991-x](attachment:9f6a894b-e5e6-4fe6-82d4-c271519a1c25:image.png)

Breast abscess. A 45-year-old woman presented with a palpable area in the right breast. Mediolateral oblique (a) mammogram shows a focal asymmetry in the upper outer breast (arrow) and associated trinagular palpable marker. Power Doppler ultrasound images (b, c) reveal two hypoechoic, oval masses with peripheral vascularity in the same region (asterisks). Axial post-contrast T1-weighted MRI (d), sagittal T2-weighted MRI (e), and postcontrast subtraction T1-weighted MRI (f) show two T2-hyperintense, rim-enhancing masses (arrows). Needle biopsy showed acute inflammatory cells consistent with abscess without evidence of malignancy

Guirguis, M.S., Adrada, B., Santiago, L. et al. Mimickers of breast malignancy: imaging findings, pathologic concordance and clinical management. Insights Imaging 12, 53 (2021). https://doi.org/10.1186/s13244-021-00991-x

BI-RADS category:

BI-RADS Imaging Scenario Recommendation
BI-RADS 3 or 4A Classic abscess with infection signs Biopsy/aspiration advised if uncertain
BI-RADS 4 Non-lactating mass with atypical features Consider malignancy and biopsy