Grading of pituitary adenomas in acromegaly. Comparison of light microscopical, immunocytochemical, and clinical data.

In a series of 284 adenomas from cases of acromegaly we studied major morphological variables using light microscopical techniques and compared them with immunocytochemical and clinical results. Using our semiquantitative estimations many inter-relationships were observed. We established the density of secretory granules, nuclear pleomorphism and the rate of occurrence of multinuclear tumour cells, as essential features of tumour differentiation. Mitotic activity and invasive growth patterns did not reveal clear dependences. Immunocytochemical analysis of 105 cases showed growth hormone (GH) in nearly all adenomas (98%), prolactin in 68%, and LH in 40%. The other hormones (ACTH, FSH, and TSH) were present at a much lower rate. Monohormonal GH-adenomas were found in only 29% of our cases. Many different combinations of hormone content could be demonstrated without any relationship to morphological or clinical data. From the linear correlations and advanced method of semiquantitative evaluation, the granular density of the tumour cells is the most useful variable for subclassification and grading of pituitary adenomas in acromegaly.