Two Diagnostic Pitfalls Mimicking a Prolactin-Secreting Microadenoma

Abstract

A 25-yr-old woman was admitted to the Neurosurgery Department with the diagnosis of a medically resistant prolactin (PRL)-secreting microadenoma. Serum PRL levels ranging between 30 and 90 ng/ml had been discovered 2 yr before in a routine gynecological assessment. Magnetic resonance imaging (MRI) disclosed an image compatible with a pituitary microadenoma (Fig. 1). The patient underwent medical treatment with cabergoline (upto0.5mg/d),withoutsignificantvariationsofbothserum PRL and neuroimaging at 1 yr. Hence, medical therapy was withdrawn. When she came to our attention, she denied any history of irregular menses and galactorrhea as well as drugs or other possible causes of hyperprolactinemia. She had had a normal pregnancy 3 yr before. Pituitary hormonal assessment documented normal values with the exception of PRL that was 54 ng/ml (normal values, 3.5–15.5 ng/ml). Testing for macroprolactin yielded positive results showing a 35% recovery, in line with the expected presence of macroprolactin. A review of the patient’s MRIs showed that the signal alteration corresponded to the insertion of a sphenoid septum and was stable also in dynamic sequences. The patient was discharged home. Macroprolactin should be suspected when a patient’s clinical history or radiological findings are inconsistent with the PRL values (1–3). A focal artifact on sellar MRI, closely related to the junction between sellar floor and sphenoidal septum, may mimic or obscure a microadenoma (4, 5). In this case, we had the association of a biochemical and a neuroradiological pitfall. The clue for a correct diagnosis was given by the patient’s history and clinical status. Acknowledgments