Oil cyst (breast)
Citation, DOI and article data
Occurs across all age and ethnic groups with a female predilection. Usually associated with blunt trauma, if present in males.
- usually asymptomatic
- tender or non-tender palpable lump
- bruising, if recent trauma
Fat debris from ruptured lipocytes tends to conglomerate to form a macroscopic pool of oil surrounded by lipid-laden macrophages or foam cells - known as an oil cyst. The wall can then calcify. Most often this occurs secondary to trauma or surgery; however, this is not always necessary.
The etiology of oil cysts is felt to be most often an end-form of liquefaction fat necrosis of the breast resulting from trauma or surgery. However, some oil cysts arise independently, without a prior history of trauma or surgery.
Specimens are usually obtained from surgical excision or aspiration. Grossly, appears as viscus, oily fluid/material.
Fat-filled macrophages and foreign body giant cells are usually present. There may be hemorrhage into fat. A fibrous capsule forms around the lipid contents. Following fatty acid saponification, there may be calcific precipitation.
Multiple intradermal oil cysts can be part of steatocystoma multiplex.
Typically seen as a radiolucent rounded mass of fat density +/- wall calcification, which if present typically appears as eggshell calcification. Lesions are usually well-circumscribed with a thin capsule. Rarely, fat-fluid levels may be present.
On ultrasound, most oil cysts are hypo-echoic with smooth walls and show neither posterior acoustic enhancement or shadowing. Echogenicity varies. Fat-fluid levels are better characterized sonographically. When present, rim calcifications will demonstrate posterior acoustic shadowing. Complex features include thick walls, mural nodularity, and internal echoic bands. A very small proportion can represent an intracystic mass.
Circumscribed, lucent, non-enhancing lesion +/- calcification.
T1WI: circumscribed, hyperintense lesion (isointense to fat)
Treatment and prognosis
Treatment is usually not required. Aspiration/biopsy is not recommended due to the inflammatory nature of oil contents.
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