In our study, we observed that E-Cadherin presented strong membranous expression in the majority of somatotroph adenomas (>70%) compared to only 27.6% of null cell adenomas whereas Cyclin-D1 was strongly expressed (expression > 50%) in 78.6 % of the gonadotroph adenomas and in 65.5% of the null cell adenomas compared to only 20% of corticotroph and somatotroph adenomas. The gene discussed is CCND1; the disease is growth hormone-secreting pituitary adenoma.