Hypothalamic neurocytoma with vasopressin immunoreactivity: Immunohistochemical and ultrastructural observations.

Hypothalamic tumors of neuronal derivation are rare. We describe the case of a 55-year-old woman with visual disturbances who was found by magnetic resonance imaging (MRI) to have a sellar and suprasellar tumor. She underwent subtotal surgical resection by a transsphe-noidal approach. By light microscopy the tumor displayed a uniform population of short spindle cells with round to oval nuclei, separated by an abundant fibrillary stroma containing axonal processes as shown by the Bodian stain. The neoplastic cells were immunoreactive for neuron-specific enolase (NSE), synaptophysin, and vasopressin, and nonimmunoreactive for glial fibrillary acidic protein (GFAP), vasoactive intestinal peptide (VIP), bombesin, chromogranin, neurofilament, cytokeratins (high and low molecular weight), vimentin, S100 protein, somatostatin, β-endorphin, galactosamine, growth hormone-releasing hormone (GRH), neurophysin, serotonin, adrenaline and noradrenaline, and corticotropin-releasing hormone (CRH). Ultrastructural features included an abundance of neurosecretory granules within neurites and perinuclear cytoplasm. Synapses and glial stroma were not demonstrable. The term hypothalamic neurocytoma delineates this neuronal tumor with distinctive histologic, immunohistochemical, and ultrastructural features. The identification of vasopressin within the tumor provides evidence of neuroendocrine function.