Cystic disease and fibroadenoma of the breast: natural history and relation to breast cancer risk.

Approximately 25% of all 'discrete' breast lesions are fibroadenomas or breast cysts and they more commonly cause a breast lump than breast cancer. Despite their frequency, their natural history and relationship to subsequent breast cancer have not been clearly defined, although it would appear that palpable breast cysts, but not fibroadenomas, are associated with some increased risk of breast cancer. The diagnosis of these two entities is now possible by fine needle aspiration and excision of these lesions is only indicated in certain circumstances.