ConditionWomen's & pregnancy health
Fat Necrosis of the Breast
Fat necrosis of the breast is a benign (non-cancerous) lump that forms when fatty breast tissue is damaged and dies, then heals with scar tissue and sometimes an oil cyst. It usually follows an injury such as a seatbelt bruise, breast surgery, reconstruction, biopsy or radiation therapy. It can feel firm and irregular and look suspicious on a mammogram, so imaging and sometimes a biopsy are needed to rule out cancer. Once confirmed, it often needs no treatment and may shrink over time.
Also called: Breast fat necrosis, oil cyst of the breast, post-traumatic fat necrosis
At a glance
- What it is
- A harmless area of damaged breast fat that heals with scarring or an oil-filled cyst.
- Common causes
- Injury (seatbelt, sports, falls), breast surgery, reconstruction, fat grafting, biopsy, radiation.
- Signs
- A firm, round or irregular lump, sometimes with bruising, skin dimpling or nipple pulling.
- Diagnosis
- Mammogram, ultrasound, sometimes MRI or a needle biopsy.
- Treatment
- Often none. Pain relief, needle drainage of an oil cyst, or removal if bothersome or uncertain.
- Cancer risk
- It does not turn into cancer and does not raise breast cancer risk.
When to get help
See a doctor within a day or two
- A red, hot, swollen breast with fever above 38 °C (100.4 °F) (possible infection or abscess)
- A rapidly growing breast lump, or one with skin changes such as an orange-peel texture, without a clear injury
Book a routine appointment
- Any new breast lump, even after a known injury or surgery
- A lump with skin dimpling, nipple pulling in or bloody nipple discharge
- A lump in a reconstructed breast or after fat grafting
- A known area of fat necrosis that is growing or changing
Usually safe to manage at home
- A lump already confirmed as fat necrosis by imaging or biopsy that is stable or shrinking
- Mild tenderness and bruising after a minor breast injury, settling within days, with follow-up if a lump remains
What fat necrosis is
The breast contains a lot of fat. When fat cells are damaged, they release oily contents and the body responds with inflammation. Over weeks to months, the area is walled off by scar tissue. The result may be:
- a firm, scar-like lump
- an oil cyst: a pocket of liquid fat surrounded by a thin wall
- calcifications (calcium deposits) visible on a mammogram
Fat necrosis can occur at any age but is more common in middle-aged women and in women with larger breasts.
Causes
- Injury to the breast: car accidents (seatbelt injuries), sports, falls or a blow. Many people do not remember the injury
- Breast surgery: lumpectomy, breast reduction, biopsy
- Breast reconstruction, especially using the person's own tissue (flaps), and fat grafting
- Radiation therapy after breast cancer
- Anticoagulant medicines, rarely
- Infection or inflammation of the breast
Symptoms
- a lump that is usually painless but can be tender
- firm, round or irregular in shape
- bruising or redness over the area in the early stages
- skin dimpling or a pulled-in nipple if scarring tightens surrounding tissue
- an oil cyst may feel smooth and mobile
These features can mimic breast cancer, which is why assessment is important.
Fat necrosis vs breast cancer and other lumps
| Fat necrosis | Breast cancer | Fibroadenoma | Breast cyst | |
|---|---|---|---|---|
| History | Injury, surgery or radiation | Often none | Young women | Ages 35 to 50 |
| Feel | Firm, irregular or smooth | Hard, irregular, fixed | Smooth, rubbery, mobile | Smooth, round, may be tender |
| Change over time | Stable or shrinks | Grows | Stable or slow growth | Can change with cycle |
| Mammogram | Oil cyst with fat center, calcifications | Spiculated mass, clustered calcifications | Well-defined mass | Fluid-filled on ultrasound |
Diagnosis
- Clinical breast exam and history of injury or surgery
- Mammogram: classic oil cysts with fatty centers and rim calcifications are reassuring and often enough for diagnosis
- Ultrasound: shows oil cysts, complex masses or scarring
- MRI: sometimes used after reconstruction or when other tests are unclear
- Needle biopsy: recommended when imaging is not clearly benign, to rule out cancer
Imaging is reported with a BI-RADS category. Classic fat necrosis is usually rated benign (BI-RADS 2). Uncertain cases may be biopsied or rechecked in 6 months.
Treatment
- No treatment is usually needed once fat necrosis is confirmed. Many lumps shrink or disappear over months
- Pain relief: a supportive bra, warm compresses, and acetaminophen (paracetamol) or ibuprofen at the label dose
- Needle aspiration: an oil cyst can be drained with a fine needle if it is uncomfortable
- Surgical removal: if the lump is painful, large, cosmetically bothersome, growing, or if a biopsy cannot rule out cancer
- After reconstruction or fat grafting: surgeons may remove or liposuction areas of fat necrosis
Outlook
Fat necrosis is harmless and does not increase the risk of breast cancer. Lumps may persist as small scars or calcifications, which future mammograms will show. Tell radiologists about any previous injury, surgery or fat necrosis so they can compare images.
Frequently asked questions
What is fat necrosis of the breast?
It is a benign lump that forms when fatty breast tissue is damaged, usually by injury, surgery or radiation, and heals with scar tissue or an oil cyst. It is not cancer and does not raise cancer risk, but it can look and feel like cancer, so it is checked with imaging.
Does fat necrosis go away?
Often, yes. Many areas of fat necrosis shrink or disappear over several months as the body reabsorbs the damaged fat. Some leave a small, permanent scar or calcification. Painful or bothersome lumps can be drained or removed.
How do doctors tell fat necrosis from breast cancer?
They combine the history of injury or surgery with mammogram and ultrasound findings. Oil cysts with fatty centers are typical of fat necrosis. If imaging is not clearly benign, a needle biopsy is done to confirm the diagnosis.
Is fat necrosis common after breast reconstruction?
Yes. It is one of the most common findings after reconstruction using your own tissue and after fat grafting. It often appears as firm areas within the reconstructed breast. Your surgeon may monitor it, or remove it if it is bothersome or uncertain on imaging.
Sources
This guide was written from current patient and clinical guidance, including:
- American Cancer Society: Fat Necrosis and Oil Cysts in the Breast
- American College of Radiology: ACR BI-RADS Atlas
- Breastcancer.org: Fat Necrosis
- American Society of Breast Surgeons: Diagnostic evaluation of breast lumps
- MedlinePlus: Breast lumps