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Breast sebaceous cyst

A breast sebaceous cyst (also sometimes known as an epidermal inclusion cyst or simply epidermoid cyst) is a benign breast lesion (BIRADS II). 

The two terms are not entirely synonymous as a sebaceous cyst has an epithelial lining as opposed to a epidermal inclusion cyst which has an epidermal lining. As far as imaging is concerned, the two entities are indistinguishable from each other 6.

For a general discussion of this entity outside the breast, please refer to epidermal inclusion cysts

The sebaceous cyst implies that the lesion originates in the sebaceous glands which is not the case and thus the term should be avoided.The epidermal inclusion cyst refers to an epidermoid cyst due to implantation of epidermal elements in the dermis. The preferred term is usually an epidermoid cyst. However, in reality, the terms are used interchangeably.

Pathology

A sebaceous cyst originates in the sebaceous gland while an epidermoid cyst, which is used interchangeably with the previous term, has its origin in the follicular infundibulum.

Location

these lesions are typically located in the skin or subcutaneous tissue. There may be a predilection towards the inframammary fold.

Radiographic features

Mammography 

They are usually seen as well-circumscribed rounded soft tissue density lesions close to the skin surface. 

Breast ultrasound

They may be often seen as small and hypo echoic and again located close to the skin surface with through transmission and with no detectable vascular flow. Hypo- and hyperechoic alternating rings may sometimes be seen on sonography. In some occasions, a characteristic track may be seen extending into the skin surface.

Doppler imaging on ultrasound may on occasion show quite remarkable "flow".  Possible low grade infection is not excluded.

Complications

  • infection - inflammation
  • cyst rupture causing a foreign-body or granulomatous reaction, or abscess formation.
  • malignant transformation into a low-grade squamous cell carcinoma is extremely rare but has been reported.

Imaging follow up

When inflammation is present - both clinical and as well as imaging follow up is advised 7

Differential diagnosis

Considerations on mammography include

On ultrasound also consder

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