In order to study the light microscopical alterations of pituitary tumours under
dopamine agonist treatment, three groups of a total of 18 large or small cell
chromophobe adenomas were analysed by light microscopical, immunohistological and morphometrical methods. They were all removed by transsphenoidal surgery. 6 of them were treated preoperatively with
dopamine agonists,
bromocriptine and/or
lisuride, for various periods of time. 8
adenomas remained preoperatively untreated. 4 additional untreated
tumors were small cell inactive
adenomas for comparison. One case was excluded from the final evaluation of the data because it appeared to be a typical non-responder, clinically as well as histologically. Immunohistological positivity for
prolactin was to be found in all cases in various degrees. Clinically active
adenomas contained many
prolactin positive cells, whereas in inactive
adenomas only scattered cells were
prolactin positive. The morphometric analysis revealed a reduction of the cytoplasmic area in a statistically significant degree in the group of
adenomas under treatment, which explains adequately the shrinkage of the entire
adenoma and the reduction of
prolactin plasma levels. The morphometric data of treated
adenomas resembled those of untreated inactive
adenomas.