Ultrastructural-morphometric effects of radiotherapy on pituitary adenomas in acromegaly.

Within a series of 22 irradiated GH-producing adenomas we studied by light microscopical and morphometrical means the grading of nuclear pleomorphism, the proportion of densely granulated cells, the number of mitoses, multinuclear cells, necrotic or necrobiotic cells, and the degree of fibrosis in comparison to non-irradiated tumours. By electronmicroscopical morphometry we investigated the changes in area, circumference, area percentage, and number of intracellular structures. The rate of necrobiotic cells and the grade of nuclear pleomorphism were significantly higher in the irradiated tumours. The fibrotic areas were larger. No differences were observed in the degree of granulation and the rate of multinuclear cells