Breast Cyst – Aspiration

Macrocysts constitute the commonest discrete benign breast mass, estimated to occur in 7–10% of all women.

Microcysts develop from apocrine metaplasia of a single lobule throughout most of reproductive life; a few go on to form macrocysts, mainly in the last decade of reproductive life.

Macrocysts fall into two broad groups: those with a persisting apocrine cell lining and active secretion/concentration of many substances; and those lined by flattened cells and metabolically much less active.

Gross cysts are associated with a small but definite increase in subsequent breast cancer, but opinions about, and evidence for, the details of the associated cancer risk are not uniform.

Simple cysts are adequately treated by aspiration; ultrasound is helpful with poorly defined cysts and to ensure complete emptying of recurrent cysts.

Cysts yielding bloodstained fluid are investigated by cytology and sonography, and warrant exploration even if triple assessment is negative. Most are due to intracystic papillary tumors of benign histology or low-grade malignancy.

Recurrent cysts may be aspirated as often as necessary, without further therapy or investigation.

Leakage from a cyst gives surrounding inflammation with altered sonographic appearances (complex cyst) and may give a residual mass after aspiration. Where painful cysts are a problem, a trial of danazol is worthwhile.

Since the increased risk of cancer is small, and most patients are in their fifth decade, standard breast screening is appropriate follow-up for most cases.

Cysts per se are not premalignant, so do not need excision, and screening should be directed at both breasts.

Galactoceles cause few clinical problems, being readily managed by aspiration. They may cause greater problems with imaging, because of the variety of appearances seen on sonography and mammography.