Fat necrosis of the breast

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Fat necrosis of the breast is a benign nonsuppurative inflammatory lesion affecting the adipose tissue. It accounts for < 3% of all breast lesions and is usually the result of trauma (including blunt injury, surgery, or radiation) to the breast. Fat necrosis of the breast manifests as an ill-defined nontender breast mass; local skin changes may also be present. Age-appropriate breast imaging is indicated in all patients with a palpable breast mass. On mammography, fat necrosis may appear as an oil cyst; on ultrasound, it may appear as a breast mass of variable echogenicity. Clinical and imaging features can resemble those of breast cancer. If there is any suspicion of malignancy or if imaging is inconclusive, image-guided biopsy is indicated. Treatment is not usually required, but surgical excision should be considered if malignancy cannot be excluded, or imaging and pathology findings are discordant.

• Incidence: < 3% of all breast lesions ^[2]
• Peak incidence: 50 years

Epidemiological data refers to the US, unless otherwise specified.

• Often associated with soft tissue trauma ^[3]
• Surgery or radiation ^[2]

• Typically manifests as an ill-defined nontender breast mass
• Often periareolar in location; can also occur peripherally
• Breast skin retraction, erythema, and/or ecchymosis

Follow age-appropriate diagnostic workup for a palpable breast mass. The findings specific to fat necrosis of the breast are described here.

Imaging findings ^[2][4][5]

• Breast ultrasound: variable; may be solid or cystic and anechoic or hyperechoic ^[5]
• Mammography ^[2][5]
  • Fluid-filled oil cyst
  • Coarse rim calcifications
  • Spiculated mass
• MRI breast with and without contrast (not routinely ordered) ^[2][5]
  • Round or oval lesions with hypointense T1 signals when fat suppression is performed
  • Irregular or spiculated mass

Image-guided biopsy

• Indication: clinical suspicion of malignancy ^[2]
• Findings ^[5][6]
  • Foam cells and multinucleated giant cells
  • Necrotic fat cells
  • Hemosiderin deposition and chronic inflammation

Imaging findings of fat necrosis (e.g., spiculated mass, calcifications) may resemble those of breast cancer. Biopsy is recommended if there is clinical suspicion of malignancy.

• Expectant management is usually sufficient.
• Appropriate surveillance for benign or probably benign lesions ^[7]
• Consider surgical excision if:
  • Malignancy can not be excluded
  • Imaging and pathology findings are discordant