Quantitative immunohistochemical assessment of clinically non-functioning pituitary adenomas

Abstract

Introduction. Immunohistochemical staining is currently the gold standard of diagnostic and classification of pituitary adenomas. However, there are some discrepancies between immunohistochemical staining results and the clinical picture of pituitary adenomas. Pituitary adenomas with positive immunohistochemical reaction might not cause any endocrinological symptoms or changes in serum pituitary hormone levels. Such a discordance may be caused partly by clinically non-functioning pituitary adenomas (CNFPAs). The aim of our study was to establish the frequency of CNFPAs and identify their histological types using quantitative immunohistochemical assessment. Materials and methods. We enrolled in the study 72 patients with pituitary adenoma, and their medical history was evaluated retrospectively. The immunohistochemical panel of anterior pituitary hormones was introduced in all cases. The immunoreactivity index was calculated manually for each specimen. Results. 36.1% patients of the evaluated group presented as CNFPAs. Among the CNFPA patients we found 38.46% cases with positive immunohistochemical reaction for one or more anterior pituitary lobe hormones. In 23.07% of cases the adenomas were monohormonal, and in 15.38% they were plurihormonal. Conclusions. The morphometric method utilising the immunoexpression index introduced in this study provided a very precise recognition of pituitary adenoma pathology. In the case of CNFPAs the immuno-histochemical staining often reveals a positive reaction also for multiple pituitary hormones. Quantitative assessment limits the subjectivity of the examiner and allows objective results comparison, so it should become a standard in histopathological assessment of pituitary adenomas.