Breast cancer is currently believed to develop through a series of well-defined stages: Normal duct > DH (ductal hyperplasia) > Atypical ductal hyperplasia (ADH) > Carcinoma in situ (CIS): DCIS/LCIS (ductal or lobular carcinoma in situ) > Invasive carcinoma (ductal or lobular). Both secreted and membrane-bound mucins have been demonstrated to be expressed during the progression from normal ducts to invasive adenocarcinoma. (+ indicates mucin detected and – indicates mucin undetected, NE not examined, £ <5% cells positive, ‡ expressed in mucinous carcinoma (in addition to ductal carcinoma), † Expressed in lobular carcinoma (in addition to ductal carcinoma), ¥ Expressed in LCIS (in addition to DCIS).