Beware of breast fibroadenomas in middle-aged women.

On first examination of 8512 Quebec area women from 40 to 59 years of age who participated in the National Study of Breast Cancer Screening, the prevalence of fibroadenoma was 8.3 per 1000. In two women, a carcinoma was discovered within their fibroadenoma--intraductal carcinoma in one and an infiltrating ductal carcinoma in the other. Clinical and histopathologic findings are described and the prognosis and treatment discussed. The peak age of women at the time of diagnosis of a fibroadenoma is in their twenties while for those with a fibroadenoma containing a carcinoma, it is in the forties. For patients under 25 years, excision can be postponed for a few months since spontaneous regression may occur and the risk of breast cancer is small at that age. For older women, treatment should not be delayed.