Invasive sellar extraventricular neurocytoma: illustrative case.

backgroundSellar extraventricular neurocytomas are exceedingly rare neuronal tumors that closely mimic more common sellar lesions, including pituitary adenomas and craniopharyngiomas. Their clinical presentation, most often visual field deficits with variable hypopituitarism, and nonspecific imaging characteristics make preoperative diagnosis difficult. Because few cases have been reported, optimal management strategies and long-term outcomes remain incompletely defined. OBSERVATIONS: A 40-year-old man presented with progressive bitemporal hemianopia, headaches, and partial hypopituitarism. MRI revealed a mixed cystic and solid sellar mass with cavernous sinus extension. He underwent endoscopic endonasal resection with the goal of maximal safe cytoreduction and optic decompression. Postoperatively, vision, headaches, and thyroid function improved. Histopathological analysis demonstrated a neurocytoma characterized by synaptophysin and chromogranin positivity, absence of pituitary hormone and glial fibrillary acidic protein expression, and a low Ki-67 proliferative index. A literature review demonstrated frequent cavernous sinus invasion and a measurable recurrence risk, particularly after subtotal resection. LESSONS: Sellar neurocytoma should be considered in the differential diagnosis of invasive sellar masses. Definitive diagnosis relies on immunohistochemical analysis demonstrating neuronal differentiation with low proliferative activity. Surgical management should prioritize maximal safe resection and optic decompression, avoiding aggressive cavernous sinus dissection. Adjuvant radiotherapy and long-term surveillance are essential when residual disease is present. https://thejns.org/doi/10.3171/CASE26205.