Endocrine Abstracts

Introduction: Sox2 is a widely expressed marker of progenitor and stem cells in various organs, strongly expressed within Rathke’s pouch and the neural ectoderm. It exerts a critical role in the early stages of pituitary development but it is still expressed in the adult gland. Sox2 expression in pituitary adenomas and its possible correlation with clinicopathologic characteristics have not been investigated so far.

Aim: To evaluate the immunohistochemical expression of Sox2 protein in pituitary adenomas.

Subjects and methods: We included in the study 34 pituitary adenoma samples (13 GH-secreting, ten prolactinomas with proven resistance to dopamine agonists and 10 non-functioning adenomas) prelevated at the time of the neurosurgical intervention. Tissue samples were analyzed by immunohistochemistry for pituitary hormones and Sox2 expression by the avidin-biotin-HRPA method.

Results: Sox2 positive expression was detected in 16 patients (47.05% of cases) and did not show an association with tumor volume or extension at diagnosis. GH-secreting tumors were immunopositive for Sox2 in 57.14% of cases, prolactinomas in 60% and non-functioning pituitary adenomas in only 20% of cases (significantly higher percentage of Sox2 positivity among secreting tumors, P=0.041). 58.82% of all patients (20 cases) had pituitary insufficiency at diagnosis. At diagnosis, the percentage of corticotrophin and gonadotrophin deficiency was significantly higher in patients with Sox2 negative tumors compared to those with Sox2 positive tumors (P=0.047 and 0.041, respectively). In cases associated with hypopituitarism, the number of endocrine pituitary axes affected was not significantly different compared to Sox2 positive tumors.

Conclusion: Sox2 positive expression is frequent in pituitary adenomas (especially in secreting tumors) but is not correlated to tumor size or invasiveness. However, intratumoral Sox2 expression is associated with a lower percentage of pituitary insufficiency.