We reviewed 95 cases of patients with pituitary microadenomas diagnosed by magnetic resonance imaging in two institutions: "Hospital Santa Cruz/Beneficência Portuguesa de Niterói" and "Clínica X-Labs/Rio de Janeiro". Our aim was to establish the main type of pituitary microadenoma, incidence and proximity to the hypophisial stalk, and correlate these findings with clinical and laboratorial data. A Philips Gyroscan T5 III (0.5 Tesla), a GE Vectra (0.5 Tesla) and a GE Signa (1.0 Tesla) scanners were used to scan the patients with rapid sequences before and after intravenous administration of paramagnetic contrast medium (gadolinium). There was a predominance of women with prolactinomas associated to galactorrhea and hyperprolactinemia. In contrast to the current literature, we observed that the pituitary stalk was centered in most cases. Contrast medium injection immediately before scanning is essential to identify microadenomas. The use of half of the preconized dose of gadolinium is recommended.

Keywords: Pituitary microadenomas. Sellar tumors. Magnetic resonance imaging.