Introduction

Fat necrosis of the breast is a benign inflammatory condition of the fatty tissue in the breast most commonly caused by trauma or breast surgery. It may present similarly to primary breast malignancy, so care must be taken to rule out this important differential. Management strategies range from follow-up imaging to excision biopsies depending on the clinical severity of the necrosis.

Epidemiology

  • Incidence: 4.00 cases per 100,000 person-years
  • Peak incidence: 50-60 years
Condition Relative
incidence
Breast abscess31.25
Breast cancer23.75
Breast fibroadenoma8.25
Fat necrosis of the breast1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Aetiology

Trauma to the breast is the main cause of fat necrosis of the breast (21-70% of cases)
  • This may be blunt force trauma (e.g. seatbelt in car accident), breast surgery (including breast conserving surgery and mastectomy with or without breast reconstruction), or biopsy.
  • Other causes include radiotherapy, anticoagulation treatment and breast infection.
  • Smoking, obesity and increasing age alongside recent surgical procedures for breast cancer all increase the risk of developing fat necrosis of the breast.

Pathophysiology

Necrosis is characterised by deranged cell death caused by inflammatory intra-cellular components, whereas apoptosis is the controlled manner in which cell death occurs after these components are isolated by other cell types.

  • In fat necrosis of of the breast, intra-cellular components spill into the interstitial space, usually following trauma, and both types of cell death result.
  • It is typically a sterile inflammatory process.
  • Early macroscopic appearances include haemorrhagic foci, ‘foam cells’ (fat-filled macrophages), and necrotic lipid material.
  • Liquefactive necrosis may occur in some cases, whereby extensive enzymatic digestion of the adipose tissue causes a cystic lesion with a liquid central cavity to form.
  • Later, fibrosis and calcification occur at the peripheries of the lesion as it resolves.

Clinical features

Fat necrosis of the breast is clinically occult in most cases. A full history and breast examination including regional lymph nodes must be done, and a general examination including vital signs.

However, frank clinical signs include:
  • Palpable mass or masses in the breast
  • These are typically ‘stony hard’ (66%), and may be adherent to the skin (50%)
  • There may be associated ecchymosis or erythema
  • A suggestive clinical history e.g. recent surgery or trauma may help the diagnosis
  • Clinical features are typically all highly suggestive of breast malignancy and fat necrosis is therefore a diagnosis of exclusion.
  • Malignancy must remain the primary differential, even if there is a clinical history of breast trauma.

Investigations

The relevant investigations are the same as those for primary breast carcinoma (i.e. triple assessment) which presents similarly and therefore must be excluded.

  • Blood tests
    • If co-existing breast infection is suspected, full blood count, U&E, CRP and blood cultures are appropriate.
  • Imaging
    • Breast ultrasound to characterise lesion
    • Mammography: may show lipid cysts, pathognomonic of fat necrosis, or areas of fibrosis or calcification indistinguishable from malignancy. Mammography may also be normal in 9% of cases.
    • MR imaging may be considered.
  • Core needle biopsy to rule out malignant pathology

Management

Patients who have undergone recent surgery or radiotherapy for breast cancer are at risk of fat necrosis, but the clinical and radiological findings of fat necrosis typically mimic those seen in breast cancer. Therefore, it is imperative to rule out cancer recurrence in these patients where fat necrosis is suspected. This requires repeat imaging and biopsy.

In patients where malignancy has been excluded:
  • If there are no troubling symptoms then follow-up with imaging and clinical examination is appropriate as the most likely course of this benign condition is normalisation of the fatty tissue without treatment.
  • In symptomatic patients, or with increasing size of benign lesion at follow-up, surgical excision is possible. Some lesions may be amenable to the less invasive vacuum-assisted biopsy for excision
  • Care must be taken at all stages to ensure that malignancy has not been missed.