FRONTIERS IN BIOSCIENCE; DUCT CELL CARCINOMA
	Adenocarcinoma of the breast may originate from the ducts or lobules. Those arising from the ducts may be present as an adenocarcinoma confined to the ducts without evidence of infiltration of the surrounding tissue (intraductal carcinoma, blue arrowheads) or as an infiltrating component (red arrowheads). In some instances the tumor may invade vascular/lymphatic channels (green arrowheads). The intraductal carcinomas consist of a uniform population of cells. These cells may fill out the entire duct lumen (solid type), may form small papillary projections into the lumen (micropapillary type), may produce small luminal structures among themselves (cribriform type) or may undergo central necrosis (comedo type). The intraductal carcinomas are divided into low grade and high grade types based on the features of the tumor cells. The high grade intraductal carcinomas show extreme heterogeneity in cell size, shape and nuclear features. On the other hand, the low grade intraductal carcinomas exhibit minimal degrees of atypia and may be associated with or without luminal necrosis. The infiltrating duct cell carcinomas are classified based on the amount of tube formation, nuclear atypia and mitosis.