Using immunohistochemistry, we have shown that NeuroD1 is expressed not only incorticotropinomas, but in fact in all study samples, including plurihormonal and null-cell pituitary adenomas, prolactinomas, somatotropinomas, mammosomatotropinomas, and gonadotropinomas. Here, NEUROD1 is linked to prolactin-producing pituitary gland adenoma.