INTRODUCTION: To the best of our knowledge, no specific chromosomal abnormalities have been found in the literature in pituitary adenomas. In the present study, we investigated 9 cases of pituitary adenoma and reviewed the current literature. MATERIALS AND METHODS: Nine cases of pituitary adenoma have been studied with immunohistochemistry and cytogenetic using short-term cultures. RESULTS: All tumors had a normal karyotype. Three cases were clinically non-secreting adenomas, three cases produced prolactin, two showed growth hormone production and one thyroid-stimulating hormone. One of the cases showed dural invasion. CONCLUSIONS: We compared our results with those published in the current literature. It appears that pituitary adenomas do not have specific numerical and structural abnormalities and mostly show a normal karyotype.