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Breast cyst

Dr Garth Kruger and Dr Jeremy Jones et al.

A breast cyst can be a relatively common cause of a breast lump in peri-menopausal women. It is a benign (BIRADS II) entity.

Pathology

They 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 masses.

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.

Radiographic features

Ultrasound

Sonographic features of a simple cyst include :

anechoic signal (no internal echoes)
smooth walls
well circumscribed shape
enchanced through transmission - posterior acoustic enhancement
sharp anterior and posterior borders
reveberation 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 transsonic with posterior acoustic enhancement in all cases. Irregular internal margins or lesions that are not smoothly circumscribed or defined are not simple cysts. See case 18519. Look carefully at case 21370 in this regard.

Additional work up

When typical features of a simple breast is seen no further work up is required. Symptomatic large cysts may warrant aspiration. If such is cyst is aspirated cytological analysis is usually not required unless in contains bloody material. Simple cyst aspiration showing straw coloured fluid can be discarded.

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

Complications form aspiration are virtually unkown buut include bleeding and theoretically infection. Aspiration of cysts can be safely done without stopping aspirin therapy.