Fat necrosis is a benign breast lesion that results from injury to the breast tissue.
- Incidence: 0.6%
- 2.75% of all benign breast lesions
- Average age at diagnosis: 50 years
- 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:
- Breast reconstruction
- Breast reduction
- Free flaps
- Fat grafting
- Silicone injections
- Radiation therapy
- Mastitis/breast infections
- Risk factors:
- Large or pendulous breasts
- Older age
Pathophysiology and Clinical Presentation
Mechanisms of injury:
- Laceration of breast tissue blood supply during procedures → ischemia → necrosis
- Traumatic hemorrhage within breast adipose tissue
- 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
- 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
- Trauma (e.g., motor vehicle accidents, assault)
- Breast surgery/biopsy
- Breast/chest radiation
- Thorough breast exam:
- Firm irregular mass, fixed to dermis
- Nipple retraction/skin tethering
- Axillary lymph node palpation: Lymphadenopathy may point toward breast cancer.
- Findings differ based on degree of fibrosis.
- May appear as a smooth-bordered lucent mass
- May demonstrate microcalcifications with areas of abnormal opacity
- 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.
- 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
- 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.
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