Simple breast cyst

Last revised by Ayla Al Kabbani on 30 Nov 2019

Simple breast cysts are a common benign cause of a breast lump in women.

Patients may be asymptomatic or present with a breast lump. Some patients may have associated pain or tenderness.

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.

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

Microcysts are found commonly in fibrocystic change.

The diagnostic sonographic features are the following:

Other findings may include the following:

  • reverberation artifact
  • smooth walls
  • peripheral calcifications

Cysts appear as a breast mass with the following features:

  • oval or round shape
  • circumscribed margins

Multiple round masses in both breasts is suggestive.

Simple cysts are benign (BI-RADS 2). When typical features of a simple breast is seen, no further workup is required.

Symptomatic large cysts may warrant aspiration. If such a situation, cytological analysis is usually not required, unless it contains bloody material 7. Simple cyst aspiration showing straw colored fluid can be discarded.

Postaspiration 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.

They should not increase in size in post-menopausal women. 

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Cases and figures

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