Imaging findings of lymphocytic hypophysitis easily misdiagnosed as pituitary adenoma

Objective To study the imaging features of lymphocytic hypophysitis in order to improve the accuracy of imaging diagnosis of the disease. Methods Imaging findings of 9 patients with lymphocytic hypophysitis admitted to Neurosurgery Department of Beijing Tiantan Hospital, Capital Medical University from January 2010 to December 2016 were retrospectively reviewed. All patients underwent laboratory examinations related to pituitary function. Except for 2 cases of slight increase in prolactin, the levels of other hormones were normal. All patients were examined with pre-contrast and post-contrast T1 weighted MR imaging and non-contrast T2 weighted MR imaging. Six patients received CT scan. Imaging diagnoses were all mistaken as pituitary adenomas. Results All cases showed diffuse enlargement of the pituitary, disappearance of neurohypophysis T1WI high signal and enlarged sella. Lesions showed iso-signal on both T1 and T2 weighted image with strong homogeneous or ring-like enhancement. Pituitary stalk was thickened in 5 cases. None of the cavernous sinus was involved in those cases. Lymphocytic hypophysitis was confirmed by pathologic examinations in all 9 patients. Conclusions Lymphocytic hypophysitis seems to have characteristic imaging findings. Compared with pituitary adenoma, lymphocytic hypophysitis does not destroy the sellar floor bone with no involvement of the cavernous sinus and it has diffuse pituitary enlargement and basically symmetrical shape. Those imaging findings of lymphocytic hypophysitis may help us improve the accuracy of imaging diagnosis. Key words: Autoimmune diseases; Lymphocytic hypophysitis; Magnetic resonance imaging; X-ray computed tomography