What is a cyst?

A cyst is a fluid filled lump.

Are they common?

Breast cysts are extremely common in women between the ages of 35 and 55 years.

Why do they occur?

They appear to be part of the normal changes that occur in the breast tissue during this time. The ducts that make up the breast start to fragment and areas of ductal tissue become isolated. The small quantities of fluid that are normally produced by the lining of the duct then build up to form a cyst.

Are they dangerous?


What symptoms do they cause?

A cyst is most often noticed when it forms a painless lump. Occasionally they become inflamed producing a warm painful area not unlike an abscess.

How are they diagnosed?

The best way to diagnose a cyst is with ultrasound. Cysts show up well as the fluid transmits sound very effectively, producing good contrast with surrounding tissue. If the cyst has any unusual features on ultrasound it should be aspirated (drained) to confirm the diagnosis.

How are they treated?

If the cyst has caused a lump or pain it can be aspirated with a thin needle under local anaesthetic in the consulting room. The process only takes a few minutes and is usually quite painless. This should be done with ultrasound guidance to allow accurate placement of the needle and to see that it collapses completely. After aspiration there should be no residual lump. A mammogram may be recommended to confirm that there are no other changes in the breast tissue such as calcification that may not show up on the ultrasound. Benign cysts do not require surgical removal.

What colour is the fluid?

Cyst fluid can vary in colour from pale green to dark brown.

Will the fluid be sent to the laboratory?

|If the clinical and ultrasound features are typical of a benign cyst and the fluid drained is not bloodstained then there is no need to send off the fluid.

Will they recur?

They may do. With the regular use of ultrasound in breast assessment we now know that cysts are frequently multiple and affect both breasts. This is not surprising as they result from involutional changes that affect all of the breast tissue. Most are impalpable, cause no symptoms and eventually disappear without any intervention.

Can I do anything to stop them forming?

Not really. We do know however, that hormone replacement therapy can increase the number and size of cysts.

Can cysts turn into cancer?

Benign cysts do not become cancerous. The biggest danger is that a solid cancerous lump may be incorrectly labelled as a cyst because it was not adequately assessed. There is an unusual condition described as intracystic cancer. This generally has quite distinctive features on ultrasound.


Do not assume that a new lump is necessarily just another cyst. It may well turn out to be but it should be thoroughly assessed with at least a clinical exam and ultrasound to confirm this.

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