Fibroadenoma.

The common breast fibroadenoma makes up between one-third and one-half of biopsies for benign breast disease. The contemporary view is that it is an abnormality of normal development and involution rather than a neoplasm. Various other benign conditions may be clinically indistinguishable, and histological confirmation was only obtained in 68% of 321 masses thought to be fibroadenomas. Short-term (13-24 mo) follow-up of 201 masses, thought to be fibroadenomas on clinical and cytological grounds, showed resolution in 31% and regression in a further 12%, this behavior being more common with single lesions; a further 32% increased in size. There have been no long-term studies, but it is likely that most regress toward the end of a woman's reproductive years. Aspiration cytology can differentiate malignant from benign disease with great accuracy, but had impaired sensitivity (87%) and specificity (76%) in differentiating fibroadenoma from other benign processes in an analysis of 244 successful aspirates. While these lesions may be safely left in women under 25 years of age, only 19 (27%) of 70 women of this age group chose this option and excision remains the most frequent treatment.