RADIOLOGY: BREAST: Case# 33605: FIBROADENOMA. 45 year old female with a palpable lump in the breast. Mammogram reveals a well circumscribed, somewhat lobular mass in the upper breast. Fibroadenoma are the most common benign solid lesion of the breast. Mammographically, fibroadenoma are well defined and usually sharply circumscribed. They may be lobulated, as in this case.