Light microscopical morphometry of prolactin secreting adenomas under treatment with dopamine agonists

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.