Pituitary adenomas.

Pituitary adenomas arise from and consist of adenohypophyseal cells. Based on the tinctorial characteristics of the cell cytoplasm, they were divided previously into chromophobic, acidophilic, and basophilic adenoma types. This classification is only of limited value, since it fails to consider the endocrine function of the adenoma cells and the cell type from which the tumor originates. Advanced morphologic techniques, including electron microscopy and immunocytology, led to a new pituitary adenoma classification reflecting current knowledge and attributing greater significance to clinical features, structure-function relationships, and cytogenesis. The morphologic study of pituitary adenomas is still in a relatively early stage and much more work is required to understand the basic principles of pituitary cytopathology. Thus, the classification used in this review may change as new facts accumulate. We feel justified to say that attempts to correlate structural features of pituitary adenomas with secretory activity and their separation into distinct entities cannot be regarded as examples of curiosity-oriented research. This type of investigation represents not only an intellectually rewarding experience, but is also of practical value and provides important information for the endocrinologists.