(a) Normal acinar architecture of human adenohypophysis as shown by the Gordon–Sweet silver technique for reticulin (magnification ×10). (b) Within adenomas, the normal reticulin fibre network is broken down (left), whereas the reticulin fiber network of the surrounding nontumorous gland (right) is stretched and condensed into a so-called pseudocapsule (Gordon–Sweet reticulin technique, magnification ×10). (c) The characteristic pattern of prolactin immunoreactivity, outlining the Golgi apparatus, is shown in a prolactin cell adenoma (magnification × 40). (d) Densely granulated growth hormone cell adenoma displaying generalized immunoreactivity for growth hormone (magnification ×25). (e) Immunostaining for cytokeratin demonstrates strong immunopositivity in the intracytoplasmic spherical fibrous bodies in a sparsely granulated growth hormone cell adenoma (magnification ×25). (f) Immunostaining for follicle-stimulating hormone demonstrates immunoreactivity as well as the characteristic pseudorosette arrangement of the polar adenoma cells of a gonadotroph cell adenoma (magnification ×25).