FRONTIERS IN BIOSCIENCE; ADENOCARCINOMA
	Adenocarcinomas are tumors that are derived from glandular structures. Such glandular structures are present within the mucosal linings of the respiratory tract, gastrointestinal tract, genital tract, urinary tract and endocrine organs. Each gland consists of epithelial cells that reside on a basement membrane. Each cell adheres to its neighboring cell by various junctions including tight junction, gap junction, and desmosome. Glands produce various secretory products. One of the most commonly found form of secretion is mucinous substances. These secretory products appear as membrane bound electron dense granules within the cytoplasm of the adenocarcinomas. Such secretions may be present within the lumen of the gland. The luminal border of the epithelial cell may exhibit microvilli or cilia. The adenocarcinomas are classified according to the extent of gland formation as well differentiated, moderately differentiated and poorly differentiated adenocarcinomas. The well differentiated adenocarcinomas largely consist of glands whereas in the poorly differentiated tumors, glands are rarely formed.