Simple breast cyst

Dr Tim Luijkx and Dr Jeremy Jones et al.

Breast cysts are a relatively common cause of a breast lump in perimenopausal women, and usually causing wage pain or discomfort and slightly tender on palpation. They are a benign (BIRADS II) entity.

Breast cysts are caused by blockage of the terminal acini with resultant dilatation of ducts. Cysts may be unilateral, although they tend to be bilateral and multifocal. Large solitary cysts appear as isolated mass. 

Cyst epithelium is cuboidal to columnar with flattening, or even atrophic change in larger cysts. Epithelial proliferation may lead to piled up masses. Epithelial overgrowth and papillary projections are not a rare finding in the cysts covered with apocrine epithelium. The stroma around the cysts represents the compressed fibrous tissue.

They can be classified according to size:

  • microcyst: <3 mm
  • macrocyst: >3 mm

Gross cysts, over 3 mm in diameter need to be differentiated from microcysts, since the microcysts are found commonly in fibrocystic change.

Sonographic features of a simple cyst include:

  • anechoic signal (no internal echoes)
  • smooth walls
  • well-circumscribed shape
  • enhanced through transmission: posterior acoustic enhancement
  • sharp anterior and posterior borders
  • reverberation artifact

They may display calcifications in their periphery. They should not increase in size in post-menopausal women. 

When a cyst contains internal low level echoes or lack some of the classical features of a simple cyst, it is then called a complicated breast cyst. Cysts are usually transonic with posterior acoustic enhancement in all cases. Irregular internal margins or lesions that are not smoothly circumscribed or defined are not simple cysts. 

When typical features of a simple breast is seen no further workup is required. Symptomatic large cysts may warrant aspiration. If such a cyst is aspirated cytological analysis is usually not required unless it contains bloody material 7. Simple cyst aspiration showing straw colored fluid, which can be discarded.

Post aspiration ultrasound confirms the cyst has disappeared completely with no residual mass and will confirm hemostasis.

Complications from aspiration are virtually unknown but include bleeding and theoretically infection. Aspiration of cysts can be safely performed without stopping aspirin therapy.

Breast imaging and pathology
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Article information

rID: 9020
System: Breast
Synonyms or Alternate Spellings:
  • Simple breast cyst
  • Breast cysts
  • Simple breast cysts

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