The analyses identified 15 cases of macroprolactinomas, two cases of microprolactinoma, one prolactin-secreting pituitary carcinoma, one GH-prolactin-secreting pituitary adenoma, and three cases of suspected microprolactinoma based on a negative CT scan, although the clinical and biochemical behavior represents a probable microadenoma. These tumors were mostly invasive in nine cases (40.1%). The gene discussed is PRL; the disease is pituitary gland adenoma.