Mammary oil cyst


  • A 45 years old lady
  • Came for screening mammogram
  • Asymptomatic
  • No family history of breast cancer
Bilateral mammogram in CC and MLO views

Mammographic findings:

  • Moderately dense breasts with symmetrical parenchymal pattern
  • A well-defined, low-density oval-shaped lesion in the right breast
  • The lesion shows thin rim/wall calcification
  • No stromal distortion
  • A few scattered benign calcifications in both breasts
  • No suspicious clustered microcalcification
  • No nipple retraction or skin thickening
  • No abnormal enlarged axillary node

Diagnosis: Mammary oil cyst (BIRADS 2: Benign)


  • Oil cyst refers to benign breast lesion where an area of focal fat necrosis becomes walled off by fibrous tissue
  • Occurs across all age and ethnic groups
  • Usually asymptomatic, can be tender or non-tender palpable lump, bruising if recent trauma
  • On mammogram it is seen as radiolucent mass of fat density, with or without wall calcification. Lesion is well circumscribed with a thin capsule. Rarely fat fluid level 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 characterised sonographically. When present, rim calcifications will demonstrate posterior acoustic shadowing.
  • Treatment is usually not required.
  • Biopsy or aspiration is not recommended.
Author: radhianahassan