HER 2

Purpose. Epidermal growth factor receptor (EGFR, HER1) and human epidermal receptor 2 (HER2) assessement in pituitary adenomas
related to hormone profile. Design and methods. For 60 retrospective cases of pituitary adenomas, we established the histopathologic
diagnosis by using morphological stains, followed by case selection for immunoprofile and EGFR and HER 2 assessement. Results.
More than one third of the studied pituitary adenomas (33,33%) were positive for HER2, with membranar pattern in basophilic cells
and with predominantly cytoplasmic, granular pattern for acidophils cells. HER2 immuno-expression characterized PRL secreting
adenomas (p=0.005) and associations between FSH-LH (p< 0.001) TSH-FSH (p=0,024) and TSH-LH (p=0.028). In situ hybridization
confirmed HER2 gene amplification in 33,34% out of all positive cases for HER2 by immunohistochemistry. EGFR positivity was found
significantly for GH-prolactin (p=0.000) and prolactin-ACTH (p=0.045) co-expressing pituitary adenomas, peritumoral macrophages
and folliculostellate cells. Conclusions. Differential HER2 and EGFR expression related to hormone profile heterogeneity can define
different subclasses of pituitary adenomas and could explain clinical, prognostic and therapeutic heterogeneity which are observed
in clinical practice. Our results support re-classification of pituitary adenomas based on molecular approach which should include
markers with well certified prognostic and therapeutic impact.