Ectopic dopamine agonist-resistant macroprolactinoma to the clivus masquerading as a chordoma - A case report.

Pituitary neuroendocrine tumors (PitNETS) are common intracranial tumors, but extrasellar or ectopic PitNETS are very rare and supposed to originate from some pituitary remnants. They are mostly found in sphenoidal sinus. But particularly, ectopic clival PitNETS are highly aggressive and can cause bone invasion and can be misdiagnosed as other lesions of the skull base such as chordomas. We report a challenging case of an ectopic prolactin-secreting PitNET arising in the clivus in a young female presenting with secondary amenorrhea and sellar mass effect symptoms. On magnetic resonance imaging (MRI), the tumor showed osteolytic features that firstly oriented towards chordoma. Regarding the very high levels of prolactin that constantly exceeded 200 ng/mL, prolactinoma was indeed very presumable. Dopamine agonist treatment was progressively introduced to its maximal tolerated dose, but with neither hormonal response nor size reduction. Hence, surgical resection was decided and the patient underwent an endoscopic transsphenoidal resection of the tumor that was purely ectopic to the clivus. The diagnosis of prolactinoma was confirmed by pathological examination and immunohistochemical staining was intensely and diffusely positive for prolactin and focally for follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The surgery succeeded to normalize prolactin level, but with residual tumor on the fourth month MRI control. Management of these rare tumors should be individualized with multidisciplinary collaboration.