Cysts

Breast cysts commonly occur in the fifth and sixth decades, with a peak incidence occurring around the age of 50. It can therefore be assumed that their etiology is related to an alteration in the overall hormonal profile of the patient. Cysts can be single or multiple and may be symptomatic or detected on mammographic screening.

Symptoms

Cysts can appear suddenly, grow to any size and may be associated with pain and tenderness. They may be single or multiple, unilateral or bilateral.

Signs

Cysts often appear as well-circumscribed, discrete, mobile lesions that may be fluctuant if they lie superficially in the breast. Alternatively, they may be much firmer if they are tense.

Radiology

Mammography
Cysts appear as well-defined soft-tissue densities. They may exhibit the "halo sign"; however, it rarely encircles the lesion completely. This is due to the fact that cysts are often obscured by surrounding breast tissue.

Simple cysts are frequently multiple and bilateral and are seen against a background of dense breast tissue. Calcification in the wall of a cyst (rim calcification) is uncommon and usually follows needle aspiration.

Ultrasound
Ultrasound is the mainstay of diagnosis and is extremely reliable in distinguishing solid from cystic masses. Cysts appear as well-defined, anechoic, thin-walled lesions. As sound travels through liquid with little attenuation, the tissue deep to a cyst appears bright (posterior enhancement). Mural lesions such as intracystic papillomas, which are only very occasionally seen, can be easily visualized using ultrasound. Some simple cysts contain inspissated material, which can make a cyst appear solid. If there is any diagnostic doubt as to whether a lesion is cystic or solid, ultrasound-guided aspiration/needle biopsy should be performed.

Pathology

Macroscopic Appearance
Cysts range in size from a few millimeters to several centimeters in diameter. They are often multiple and may be bilateral. The cyst wall may be smooth, thin and glistening or thickened and fibrotic due to the presence of granulation tissue and inflammation invoked by previous rupture. The cyst contents may be thin, straw-colored fluid or thick green-to-brown material, indicating the presence of inflammatory cells or altered blood within the cyst fluid.

Microscopic Appearance
The cyst lining is usually composed of flattened ductal epithelial cells or apocrine metaplastic epithelium that may show papillary projections. Foamy macrophages are frequently present in the cyst lumen and may also be seen infiltrating the lining epithelium if it is ductal in type.