IS Case 234: Traumatic oil cysts

Trushar Sarang, MD

Imaging Sciences URMC 2008
Publication Date: 2009-05-22


Patient is a 55-year-old female with no personal or family history of breast cancer. She reports a motor vehicle accident nine years ago with injury to the right breast.


Multiple right breast oil cysts.


Traumatic oil cysts


Oil cysts are a common benign finding found during routine screening mammography. They are formed by fat necrosis of the normal fat cells who lose their nuclei usually due to trauma or surgery. The extracellular fat is then phagocytized by histiocytes initiating a fibrotic response and eventual peripheral calcification. The centers of the cysts are composed of liquefied fat and the periphery is a thin layer of calcification, forming the characteristic "egg-shell" appearance on mammography. It is important not to ignore any adjacent emerging microcalcifications that can be obscured by these benign calcifications, especially after surgery for breast cancer.

The differential diagnosis includes steatocytoma multiplex, lipomas, and galactoceles. Lipomas are often difficult to distinguish from the surrounding breast lobules. Galactoceles are extremely rare and often present in pregnant and post-partum females. Steatocytoma multiplex is a rare disorder where oil cysts form in the sebaceous skin tissue, not the fatty breast parenchyma.

There is no association with malignancy. Ultrasound and MRI can be used for further evaluation. If needed, the cyst can be aspirated.


  1. # Brant WE, Helms CA. Fundamentals of Diagnostic Radiology. 3rd ed., Lippincott Williams and Wilkins, 2007.
  2. Stephens TW, Whitman GJ, Stelling CB. Typical benign calcifications of the breast that do not require biopsy. The Radiologist. 2003;10:1-9.
  3. Miller JA, Festa S, Goldstein M. Benign fat necrosis simulating bilateral breast malignancy after reduction mammoplasty. South Med J. 1998 Aug;91(8):765-7. [PMID: 9715227]

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