Pituicytoma (pilocytic astrocytoma). Case report.

Tumors of the posterior pituitary are rare and the previous nomenclature has been confusing. A 40-year-old man presented with visual failure and disconnection hyperprolactinemia (830 mU/liter) due to a large invasive pituitary tumor shown to be a pituicytoma (pilocytic astrocytoma). Its astrocytic nature was confirmed by positive immunostaining for glial fibrillary acidic protein and the finding of cytoplasmic filaments on electron microscopy. This case report contains the pathological description of a pituicytoma and illustrates that a non-adenomatous pituitary lesion may masquerade as a pituitary adenoma. Large pituitary lesions associated with serum prolactin concentrations of less than 3000 mU/liter require early surgical biopsy.