Association of breast cysts and breast cancer.

A review of 915 consecutive patients with breast cancer and 812 with breast cysts showed that an association between the two is uncommon--5% of breast cancers were associated with cysts and 4% of cysts were associated with breast cancer. Four types of association were identified: (a) cystic cancers--easily diagnosed because of the characteristic features of the aspirate, failure of the mass to disappear and early recurrence in a patient whose age and menstrual status were not usually associated with cysts; (b) cancers occurring simultaneously with breast cysts--recognized because they did not contain cyst fluid; (c) cysts occurring after breast cancer--diagnosed by aspiration of the mass in premenopausal women; (d) cancers in patients who have had breast cysts--usually occurring many years after the cyst aspiration when menses had ceased. These associations were not sufficiently frequent to justify specific follow-up, but all suspected cysts should be successfully aspirated to confirm the clinical diagnosis.