Ductal and lobular carcinoma in situ arising within an enlarging biopsy proven fibroadenoma.

The diagnosis via core needle biopsy of concurrent ductal carcinoma in situ and lobular carcinoma in situ within an enlarging previously biopsied benign fibroadenoma in women in their 40s is rare. Several case reports have described the occurrence of malignant changes within fibroadenomas, usually as an incidental finding following excision, and few reports have documented the transition of a fibroadenoma to malignancy. The current case report emphasises the importance of re-biopsying enlarging fibroadenomas, even with otherwise maintained benign appearing features on imaging, in women in their 40s, in order to exclude the possibility of malignancy.