[An immunohistochemical and ultrastructural study of granular cell tumor of the neurohypophysis].

We describe the histopathological examination of a granular cell tumor of the neurohypophysis (GCTN). The immunohistochemical study revealed a focal positivity for GFAP within rare neoplastic cells. The electron microscopy study characterised two types of cells: some contained spindles of intermediate filaments and a few granules in their cytoplasm whereas others cells only contained granules. These findings are compatible with the astrocytic origin of the GCTN, which have been suggested by many authors but never proved up to day.