The three major cell types are identified on the basis of their staining reactions.
1. Acidophils - 40%, heavily stained, bright red cytoplasma in H&E.
2. Basophils - 10%, paler-staining cytoplasma, blue-ish in H&E.
3. Chromophobes - 50%, only the nucleus is stained in H&E. The cytoplasm doesn't stain.
Note: the cells within the pars distalis are arranged in thick cords, with different cell types intermingled.