Stem Cell Transcription Factor Sox2 Is Expressed in a Subset of Folliculo-stellate Cells of Growth Hormone-Producing Pituitary Neuroendocrine Tumours and Its Expression Shows No Association with Tumour Size or IGF1 Levels: a Clinicopathological Study of 109 Cases.

Sox2 is one of the transcription factors responsible for the maintenance of stem cell phenotype. It has been implicated as a marker of stem cells in normal pituitaries and pituitary neuroendocrine tumours. To explore the clinical significance of Sox2 expression in histological sections, we performed immunohistochemical detection of Sox2 in 113 pituitary neuroendocrine tumours from 109 patients with acromegaly. In 11 tumours, we performed double immunostaining for Sox2, annexin A1 and S100 protein. Tumours were characterised using the WHO classification system. Proliferative activity and invasion were assessed. The amount of immunoreactive cells was evaluated and correlated with tumour size and biochemical features (levels of IGF1, GH, prolactin, βTSH). Sox2