Electron microscopical morphometry of pituitary adenomas. Comparison of tumours in acromegaly and hyperprolactinemia.

By electron microscopical morphometry (point counting method) 4 groups of adenomas were compared in order to identify the source of prolactin in hyperprolactinemia. The 4 types of adenomas were characterized by the following features: Group I: acromegaly without hyperprolactinemia (GH positive and PRL negative on the immunohistochemical level); Group II: acromegaly with hyperprolactinemia and/or galactorrhea (GH positive and PRL positive on the immunohistochemical level); Group III: adenomas with hyperprolactinemia without acromegaly (GH negative and PRL positive on the immunohistochemical level); Group IV: adenomas with hyperprolactinemia without acromegaly (GH and PRL negative on the immunohistochemical level). Morphometry was performed in order to analyse the relative amount of the following cellular structures: nuclei, nucleoli, rough endoplasmic reticulum, Golgi fields, immature secretory granules, mature secretory granules, lysosomes, mitochondria, unorganized cytoplasm, and cellular membranes. Significant differences (Student t-test, Wilcoxon test; 2 p less than 0.05) were found for the following compartments: rough endoplasmic reticulum and Golgi fields in group III had significantly larger volumes than in group IV. The volume of secretory granules of group II and group IV was larger than of group III. The volume of mitochondria of group IV was larger than in group I, and it was larger in group I and group III than in group II. Despite these differences a distinctive morphometrical pattern of the different subgroups could not be established. The quantitative data are valuable for interpretation of high or low functional activity but not for differential diagnoses. Therefore, if only the source of PRL in hyperprolactinemia has to be identified, immunocytochemistry is the best and simpler method.(ABSTRACT TRUNCATED AT 250 WORDS)