Figure 1.

Light microscopic characteristics of pituitary adenomas. A. Sparsely granulated somatotroph adenomas are composed of chromophobic cells that contain eccentric nuclei, which are pushed to the cell periphery and indented by fibrous bodies (arrows). B. Acidophil stem cell adenomas are composed of eosinophilic “oncocytic” cells that exhibit cytoplasmic vacuolization because of mitochondrial dilatation and giant mitochondria. C. Densely granulated corticotroph adenomas and silent corticotroph type I adenomas are composed of tumor cells with basophilic cytoplasm due to the numerous adrenocorticotropic hormone‐containing secretory granules. D. Perivascular pseudorosette formation and a pseudopapillary appearance are characteristic features of gonadotroph adenomas.