Symptomatic granular cell tumor of the neurohypophysis

Symptomatic granular cell tumors of the neurohypophysis or infundibulum are very rare neoplasms which are difficult to diagnose before operation. We report a case of symptomatic granular cell tumor of the neurohypophysis in a 36-year-old woman who had suffered from amenorrhea and general malaise for more than 1 year. No definite visual or neurological deficit was found. Laboratory examination revealed hyperprolactinemia and decrease of other pituitary hormones. T1-weighted magnetic resonance imaging (MRI) revealed an isointense sellar mass with suprasellar extension. Transsphenoidal subtotal tumor removal was performed and pathological examination revealed a granular cell tumor of the neurohypophysis composed of densely packed polygonal cells with abundant eosinophilic, granular cytoplasm. The granules were periodic acid-Schiff-positive and diastase-resistant. Immunohistochemical study showed positive reaction for S-100 protein and antitrypsin antibodies. Electron microscopic examination showed numerous lysosomes in the cytoplasm of tumor cells. The postoperative MRI showed the residual tumor to be just behind the pituitary stalk and that the tumor should arise from the posterior lobe of the pituitary gland. The postoperative course was smooth and there were no sequelae during 30 months of regular follow-up. We believe surgery remains the treatment of choice and even partial removal of the tumor may benefit the patient.