Fat Necrosis of the Breast

Fat necrosis of the breast is an inflammatory, benign condition resulting from injury to the breast tissue. Forms of injury include blunt traumatic injury as well as trauma from surgical procedures, biopsies, and radiation therapy. Fat necrosis of the breast is characterized by the presence of an ill-defined breast mass that is usually accompanied by overlying skin changes. Oil cysts may also form as fibrosis and calcification trap oil from degenerating fat cells. Fat necrosis of the breast may be clinically and radiographically difficult to distinguish from a malignant mass. Diagnosis relies on a history consistent with trauma, breast imaging, and, less commonly, a core needle biopsy for definitive diagnosis. Treatment is usually not required. The primary clinical significance of this condition is its possible confusion with breast cancer on exam and imaging.

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Overview

Definition

Fat necrosis is a benign breast lesion that results from injury to the breast tissue.

Epidemiology

  • Incidence: 0.6%
  • 2.75% of all benign breast lesions
  • Average age at diagnosis: 50 years

Etiology

  • Trauma:
    • Direct injury to the chest (including abuse)
    • Up to 50% of patients may not report/recall trauma.
  • Fine and core needle breast biopsies
  • Surgical procedures:
    • Lumpectomy
    • Breast reconstruction
    • Breast reduction
    • Mastectomy
    • Free flaps
    • Fat grafting
  • Silicone injections
  • Radiation therapy
  • Mastitis/breast infections
  • Risk factors:
    • Large or pendulous breasts
    • Older age
    • Smoking
    • Obesity

Pathophysiology and Clinical Presentation

Pathophysiology

Mechanisms of injury:

  • Laceration of breast tissue blood supply during procedures → ischemia → necrosis
  • Traumatic hemorrhage within breast adipose tissue

Tissue response:

  • Aseptic saponification:
    • Fatty acids are released from triglycerides by the blood or tissue lipase. 
    • Fatty acids form a complex with calcium (calcification).
    • Reactive inflammation around saponified tissue results in fibrosis and scarring.
  • Another mechanism is cystic degeneration:
    • Adipose cells release their contents.
    • Calcification and fibrosis can form around the degenerated fat → oil cysts

Clinical presentation

  • Firm, irregular breast mass (mimics breast cancer)
  • May be tender, painful, or painless
  • Usually located in the periareolar area, but may occur anywhere on the breast
  • May be accompanied by erythema and/or ecchymosis
  • Skin or nipple retraction
Fat necrosis of the right breast

Fat necrosis of the breast with an area of skin necrosis secondary to injection of methylene blue dye

Image: “Skin and fat necrosis of the right breast” by St Georges Hospital, London, UK. License: CC BY 2.0

Diagnosis

History

  • Trauma (e.g., motor vehicle accidents, assault)
  • Breast surgery/biopsy
  • Infections/mastitis
  • Breast/chest radiation

Physical exam

  • Thorough breast exam:
    • Firm irregular mass, fixed to dermis
    • Nipple retraction/skin tethering
  • Axillary lymph node palpation: Lymphadenopathy may point toward breast cancer.

Imaging

  • Mammogram: 
    • Findings differ based on degree of fibrosis.
    • May appear as a smooth-bordered lucent mass
    • May demonstrate microcalcifications with areas of abnormal opacity
  • Ultrasonography:
    • Less specific than mammography
    • Increased echogenicity of subcutaneous tissue
    • Hypoechoic, anechoic, or solid mass
    • Oil cysts: 
      • Cystic lesions with echogenic internal bands
      • Wall calcifications
  • Breast magnetic resonance imaging (MRI):
    • May be helpful in cases with significant fibrosis
    • Differentiates fat necrosis from carcinoma
    • Fat necrosis usually appears identical to adjacent fat on MRI.
G3 fat necrosis

Mammography demonstrating fat necrosis

Image: “G3 fat necrosis” by Department of Radiation Oncology, Laboratory of Medical Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy. License: CC BY 2.0

Management

  • Observation and reassurance
  • Natural history: Lesions may enlarge, remain unchanged, or regress.
  • Surgical management usually not required, but may be chosen if the mass:
    • Does not resolve
    • Causes pain
    • Causes undesirable breast distortion
  • Aspiration of oil cysts with a needle if the cysts cause discomfort

Differential Diagnosis

  • Breast cancer: the most important diagnosis to rule out when a patient presents with a breast mass or evidence of calcifications and fibrosis on imaging, as fat necrosis may present in a very similar way. If the diagnosis cannot be made based on imaging alone, core needle biopsy is required. Management may involve surgery, chemotherapy, radiation, and hormonal treatment.
  • Fibrocystic changes of the breast: a non-specific term referring to several types of benign breast conditions that usually occur as a result of cyclic hormonal stimulation from estrogen and progesterone. The most common types of changes are non-proliferative lesions including cysts within the ducts and fibrosis resulting from chronic inflammation after these cysts rupture. Diagnosis is made with mammogram and ultrasound imaging. Treatment is supportive.
  • Mastitis and/or breast abscess: inflammation of the breast tissue, most commonly due to infection with skin or oral flora introduced during breastfeeding. A purulent abscess may form. Occasionally, non-lactational mastitis and abscesses are also possible. Cases usually present with a fever and pain, erythema, and edema of the breast, with or without a tender fluctuant mass (abscess). Management involves antibiotics, continued expression of breast milk if lactating, and incision and drainage of an abscess.
  • Galactocele: a cystic collection of fluid usually caused by an obstructed milk duct. A galactocele presents as a palpable, firm mass in the subareolar region and may show a classic fat-fluid level on imaging. Diagnosis is based on history and aspiration, yielding milky fluid. These lesions do not require excision.
  • Fibroadenoma: a benign solid breast mass composed of fibrous and glandular tissue, which presents as a small, well-defined, mobile mass with a rubbery or firm consistency. The exact etiology is unknown. Diagnosis is confirmed with a core needle biopsy. Management is either excision or observation.
  • Phyllodes tumor: a fibroepithelial tumor similar to fibroadenomas, usually characterized by rapid growth. These tumors may behave like benign fibroadenomas or may become malignant and metastasize. Phyllodes tumors are associated with Li-Fraumeni syndrome. Diagnosis is by core needle biopsy and management involves complete resection, with adjuvant radiation in malignant cases.

References

  1. Laronga, C., Tollin, S., and Mooney, B. (2019). Breast cysts: clinical manifestations, diagnosis, and management. In Chen, W. (Ed.), UpToDate. Retrieved February 3, 2021, from https://www.uptodate.com/contents/breast-cysts-clinical-manifestations-diagnosis-and-management
  2. Lester, S.C. (2005). The breast. In Kumar, V., Abbas, A.K., and Fausto, N. (Eds). Robbins and Cotran Pathologic Basis of Disease (7th ed., pp. 1127).
  3. Genova, R. (2020). Breast fat necrosis. In Garza, R. (Ed.), StatPearls. Retrieved 3 February  2021 from https://www.statpearls.com/articlelibrary/viewarticle/21634/ 
  4. Sabel, M.S. (2020). Overview of benign breast disease. In Chen, W. (Ed.), UpToDate. Retrieved 3 February 2021, from https://www.uptodate.com/contents/overview-of-benign-breast-disease

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