-Most common benign tumor; age 20-30
-Hormonal responsive, increasing during pregnancy, can be complicated by infarction.
-Oval, white, rubbery, MOBILE mass.
-Well circumscribed, sharply demarcated from surrounding tissue.
-Hyalinized or myxoid stroma compress epithelium
-Arise from intralobular stroma of the TDLU involved (TDLU = Terminal duct, lobular unit)
Histology: stretched of ducts, can be shelled out - don't see any benign breast tissue so likely excised entirely