Fat necrosis within the breast is a pathological process that occurs when there is saponification of local fat. It is a benign inflammatory process and is becoming increasingly common with greater use of breast conserving surgery and mammoplasty procedures.
Most at risk are middle-aged women with pendulous breasts. The onset of fat necrosis can be considerably delayed, occurring 10 years or more after surgery 3.
At a microscopic level, the initial change is disruption of fat cells where vacuoles with the remnants of necrotic fat cells are formed. They then become surrounded by lipid-laden macrophages, multinucleated giant cells, and acute inflammatory cells. Fibrosis develops during the reparative phase peripherally enclosing an area of necrotic fat and cellular debris. Eventually, fibrosis may replace the area of degenerated fat with a scar, or loculated and degenerated fat may persist for years within a fibrotic scar.
Causative factors include
- direct trauma e.g. from a seat belt, breast biopsy, implant removal, prior reconstruction. In everyday practice, trauma and surgery are the most common causes.
- nodular panniculitis - Weber-Christian disease
When there is calcification within the cyst wall it is termed liponecrosis macrocystica calcifcans.
There is a predilection towards the subareolar and periareolar regions.
Fat necrosis can have a very variable, sometimes alarming, appearance on mammography and is often potentially confusing to the novice breast imager. Initially, it can be seen as an ill-defined and irregular, spiculated mass-like area. Associated calcification can be seen, which can mimic that of more malignant entities such as DCIS. Note that fat necrosis of the breast can change with time with progressive calcification so comparison with previous imaging is essential. Also, the changes can often be seen and correlated with the position of surgical scarring on the breast itself (refer to the technologist sheet). The calcification of fat necrosis is typically peripheral with a stippled curvilinear appearance creating the appearance of lucent "bubbles" in the breast parenchyma. Note the low density centres. Tumour formation is not a part of fat necrosis although it may be clinically palpable.
With time, it becomes more defined and well-circumscribed giving rise to an oil cyst. Oil cysts can have very fine curvilinear calcification of the walls. The centre of the lesion becomes increasingly homogenous with fat-density. The cyst wall calcify in ~ 5%.
May be seen as a hypoechoic mass with well defined margins + / - mural nodule(s). The identification of the subtle wall nodularity in an oil cyst is a dead giveaway but takes effort and real time imaging. Ultrasound of fat necrosis should always be interpreted in the context of mammographic findings.
Aspiration of an oil cyst shows typically a milky, emulsified fat appearance. In the sample bottle the fat globules can be seen drifting on the Cytolyt beofre they disperse. Typical appearance and immediately recognisable.
On ultrasound, the lesion may occasionally represent an intracystic carcinoma and mammographic correlation is recommended in these circumstances 1. The key to diagnosis is the history, the tech sheet and review of multiple cases. On ultrasound an oil cyst and seroma are often indistinguishable.
- 1. Harvey JA, Moran RE, Maurer EJ et-al. Sonographic features of mammary oil cysts. J Ultrasound Med. 1997;16 (11): 719-24. J Ultrasound Med (abstract) - Pubmed citation
- 2. Bargum K, Nielsen SM. Case report: fat necrosis of the breast appearing as oil cysts with fat-fluid levels. Br J Radiol. 1993;66 (788): 718-20. doi:10.1259/0007-1285-66-788-718 - Pubmed citation
- 3. Pope TL. Aunt Minnie's Atlas and Imaging-Specific Diagnosis. Lippincott Williams & Wilkins. (2008) ISBN:0781787815. Read it at Google Books - Find it at Amazon
- 4. Soo MS, Kornguth PJ, Hertzberg BS. Fat necrosis in the breast: sonographic features. Radiology. 1998;206 (1): 261-9. Radiology (abstract) - Pubmed citation
- 5. Taboada JL, Stephens TW, Krishnamurthy S et-al. The many faces of fat necrosis in the breast. AJR Am J Roentgenol. 2009;192 (3): 815-25. doi:10.2214/AJR.08.1250 - Pubmed citation
- 6. Bilgen IG, Ustun EE, Memis A. Fat necrosis of the breast: clinical, mammographic and sonographic features. Eur J Radiol. 2001;39 (2): 92-9. Eur J Radiol (link) - Pubmed citation
- 7. Kinoshita T, Yashiro N, Yoshigi J et-al. Fat necrosis of breast: a potential pitfall in breast MRI. Clin Imaging. 26 (4): 250-3. Clin Imaging (link) - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Breast fat nacrosis||✗|
|Traumatic fat necrosis of the breast||✗|
|Fat necrosis of the breast||✗|
|Fat necrosis (breast)||✗|