FRONTIERS IN BIOSCIENCE; MUCIN
	Glandular cells synthesize various secretory products into the glandular lumen (L). Demonstration of the mucinous substances is the common practice for defining the glandular origin of the adenocarcinomas. Prior to secretion into the glandular lumen, these products are formed as membrane bound granules containing electron dense secretory products (pink arrowheads) within the cytoplasm of the epithelial cells. Blue arrowheads point to the microvilli on the surface of the epithelial cells. The tight (green arrowhead), gap (red arrowhead) and desmosome (brown arrowhead) are seen between opposing plasma membranes of the epithelial cells.