Micko ASG, et al. - The purpose of this study was to analyze the prognostic value of MGMT and MSH6 immunoexpression for aggressive functioning pituitary adenomas. The data indicated that low-to-moderate O6-methyl-guanine-DNA methyltransferase immunoexpression was the only marker that significantly associated with surgical invasiveness and recurrence in functioning pituitary macroadenomas. Thus, in the future, MGMT status may be considered an additional marker for understanding the biological behavior of pituitary adenomas.