Simple Breast Cysts

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Breast cysts are extremely common.  The incidence of cyst formation increases after the age of thirty years and peaks in the early fifties, which is the average age of menopause of women in the U.K.  The prevalence of cysts then falls and is uncommon after the age of 60 years.  However, with increasing use of Hormone Replacement Therapy (HRT), the prevalence of breast cysts is persisting into a later age group.

Cysts may be single or multiple and may affect one or both breasts.  While symptomatic cysts may be the reason for referral or presentation to a specialist breast clinic, there are many women in the community who have cysts without even knowing that they are there.  These cysts may range in size from very small, say 1mm in diameter to large palpable cysts several centimetres in diameters that are easily felt.  A simple breast cyst is a single fluid filled cavity.  When cysts are lax they adopt an oval shape, but as they become tense, cysts  become round.  Most cysts do not cause any symptoms.  However when large, cysts may be felt as lumps that can become painful when tense. In some women, multiple large cysts may form in either breast.

Pathological features

Breast cysts usually arise within ducts that twist and fold, to form a discrete structure.  Cysts are usually filled with straw coloured, yellow, green, brown or black coloured fluid.  The lining of cysts probably actively secrete the fluid component.  There is no proven link of simple breast cysts to cancer risk.  In general terms, if cysts are established to be benign on special investigations, there is no predisposition to cancer.  If however any atypical abnormality is detected on clinical assessment or special investigations, it may be advisable to have the area biopsied or even excised surgically.  Examples are: (i) if aspiration of the cyst fluid is blood stained; (ii) a lump persists despite aspiration; or (iii) if the cells retrieved look abnormal under the microscope.   Typical cyst fluid without any adverse features is usually discarded without any need for further cell assessment. 

Natural History

Breast cysts probably form under hormonal influence.  New cyst formation is unusual once a true menopausal state has been established.  Cysts may therefore come and go depending upon active circulating hormone levels and the ability of breast tissue to respond.  Once the diagnosis is established, cysts may be left alone and simply monitored by observation.  If a cyst becomes symptomatic, for example if it forms a tender breast lump, it can be re-aspirated.  However if there are multiple cysts in both breasts, clinical judgement has to be exercised, as aspirating cysts simply because they are there may not be practical.  This is particularly true if they cannot be felt and if they are only visible on ultrasound examination.

Cysts may form as part of general fibrocystic change within both breasts.  A separate leaflet for this is available.  An important component of follow up is breast awareness and self-examination.  Even if you have been diagnosed to have breast cysts or fibrocystic change and a new lump forms you will still need to have this assessed.  This is because new cysts need to be distinguished from solid lumps.  Cystic change may coexist with a variety of other breast conditions. Most of these are managed conservatively without the need for surgery.

If your are unsure of any new changes on self-examination you should report this to your specialist.

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