Pituitary histology

The adenohypophysis is the front part of the pituitary gland, and under the microscope you recognize it by its well-defined acini: clusters of cells with clear borders, each cluster holding a mix of cells that produce different hormones.

Telling them apart takes stains, which are dyes that stick to some things and not to others. Think of a marker that soaks into porous paper but slides right off a laminated sheet: the color stays where there is something to grab onto. Hematoxylin and eosin, along with PAS-OG preparations, bring out three cell types, and the criterion is simply color. Acidophils usually store polypeptide hormones, and their cytoplasm, the inside of the cell, stains red or orange. Basophils stain blue or purple and store glycoprotein hormones. And chromophobes, whose name means they shy away from color, do not stain, because their hormone content is minimal or absent; many are thought to have been acidophils or basophils that already let go of their granules and were left empty.