Prothymosin-alpha and Ki-67 expression in pituitary adenomas

Prothymosin alpha (PTMA), a nuclear oncoprotein involved in cell cycle regulation, is used as a prognostic marker in many cancers. The histopathology of pituitary carcinomas and locally invasive adenomas is indistinguishable from that of benign tumors. A new marker is needed to differentiate these lesions. We evaluated PTMA in pituitary adenomas to determine its usefulness as a prognostic factor of tumor proliferation.

We conducted a retrospective analysis of a group of 27 patients, including 15 females (56%) and 12 males (44%) with a mean age of 58.6±12 years, who underwent pituitary tumor surgery between 2003 and 2012. The Ki-67 and PTMA-nuclear (PTMA-n) and PTMA-cytoplasmic (PTMA-c) indices were determined by immunohistochemical staining. We studied histopathological features, clinical symptoms, and magnetic resonance imaging or computed tomography performed before surgery and one year following surgery to evaluate tumor size and progression.

The expression of Ki-67 was revealed in 77.8% of adenomas, PTMA-n in 81.5% and PTMA-c in 92.6%. The mean value of the Ki-67 index was 1.8%, PTMA-n was 1.84%, and PTMA-c was 35.6%. There was a significant positive correlation between Ki-67 and PTMA-n (p=0.009). We did not find any correlation between Ki-67, PTMA-c, and tumor progression. PTMA-n was found to be correlated with tumor size (p=0.045) and was higher in the case of gonadotropinomas (p=0.026).

The positive nuclear expression of Ki-67 and PTMA was observed in the majority of pituitary adenomas. Neither the expression of Ki-67 nor that of PTMA-c was related to tumor recurrence or local invasion.