Breast Cysts
Cysts in the breast are a common, benign entity that are frequently diagnosed incidentally during breast imaging, although they can sometimes cause symptoms such as a lump. While the role of imaging and biopsy of a cyst is to confirm that is indeed what the lesion is, it is important to emphasise that cysts are not cancerous and having cysts does not significantly increase the risk of having a breast cancer.
Cysts are fluid-filled sacs in the breast which can be single or multiple. They may come and go and change size with the menstrual cycle. They form when the amount of fluid being produced by the duct linings of the breast cannot be absorbed adequately because of a blocked duct, or the volume produced exceeds absorption capacity.
While it isn’t clear why some women form cysts while others do not, their cause is believed to relate to hormone factors. They are very common and are found in up to half of women presenting to a breast clinic. While they can occur in women of any age, they are most commonly seen in the 30-50 year old age group.
Diagnosis
Often the diagnosis of a simple cyst can be made from the appearance seen on mammogram and/or ultrasound. On mammogram they appear as smooth and round while on ultrasound they are smooth, round and black because of the fluid filling the cyst. These are referred to as ‘simple cysts.’ If the cyst does not have these typical features, further investigations such as a needle biopsy may be ordered by your doctor to confirm the diagnosis. Occasionally a needly biopsy is also indicated to treat the symptoms a cyst may be causing. In this situation, you may hear the cyst being referred to as a ‘complex cyst.’
Occasionally the cyst may become large and cause a lump to form. This lump may be tender; even in tissue where there are smaller cysts this can also cause a tenderness to the area. Clinically, the lump will be smooth and round but it can be quite tense if there is an amount of fluid under pressure.
Treatment
Most cysts require no treatment and provided they have a typical appearance, require no follow up.
When there is lack of certainty about a cyst diagnosis, for example if the cyst has a solid appearance, then further testing with a cyst drainage may be indicated. This involved putting a needle into the cyst to drain the fluid under ultrasound guidance. Often there is watery fluid in the cyst, although sometimes it may appear more gluggy or pasty. The radiologist may sent the fluid for further testing. This is not a reason for concern; often the reason for this is to simply confirm the lesion is a cyst.
Rather than perform a cyst aspiration, your doctor may recommend a repeat ultrasound after a number of months, particularly if there are several lesions. This approach is called ‘short interval follow up.’
Surgery is rarely indicated for cysts. Only those which recur after drainage or those with concerning features on imaging which warrant a more definitive tissue diagnosis with a surgical biopsy require an operation.
Follow up
Cysts can recur and they can develop in other parts of the breast. Once aspirated they typically take several weeks to re-fill, if they re-fill at all.
Cysts and cancer
Cysts often cause worry because they can cause symptoms that may be attributed to a cancer such as a lump and there may be uncertainty about their diagnosis. While simple cysts are definitely not cancer and safe to leave alone, there is a rare type of cancer called an intracystic cancer that can develop inside a cyst. It is important to emphasise that such cysts look abnormal on imaging and behave differently once they are aspirated.
More concerningly, people who had numerous cysts may become complacent if they develop a new breast lump. It is of paramount importance that every new breast lump is investigated appropriately.
