Background:Neuroendocrine tumors (NET) originate from the diffuse neuroendocrine system. These can arise in almost every organ of the body, although they are most commonly found in the gastrointestinal tract and respiratory system. The skull base and sellar region are extremely rare sites for neuroendocrine carcinoma. Consequently, in this case, both diagnosis and definition of surgical goals, as well as further treatment strategies were challenging.Case Description:A 65-year-old woman was admitted to our Neurosurgery Department with a rapidly progressive visus reduction, drowsiness, polyuria, and polydipsia. Neuroimaging showed a sellar/suprasellar mass (diameter of 2 cm) with a heterogeneous signal compressing the optic chiasm and extending laterally toward the cavernous sinus. Differential diagnosis based on imaging included pituitary macroadenoma or metastasis. The patient underwent endoscopic endonasal transsphenoidal surgery. A total resection of the mass was impossible because of the infiltration of the optic chiasm and the intraoperative histological diagnosis of malignant epithelial neoplasm. Further histological evaluation revealed that the lesion was a NET with no other primary or metastatic sites detectable. Subsequently, the patient was successfully treated with fractioned stereotactic radiotherapy and polychemotherapy. Four years after the surgery, follow-up magnetic resonance imaging showed stability of the residual disease. Neurologic examination revealed a complete visual recovery.Conclusions:Primary pituitary NET, though rare, should be included in the differential diagnosis of sellar lesions. A multimodality treatment approach is needed. Finally, the present case highlights, that in the case of a pituitary lesion infiltrating the optic chiasm, including NET, the endoscopic endonasal transsphenoidal subtotal resection followed by fractioned stereotactic radiotherapy and chemotherapy may represent an effective and safe choice of treatment.