Suprasellar germinoma: intraoperative findings from an endoscopic endonasal approach. Illustrative case.

backgroundIntracranial germinomas are rare tumors, yet they are the most frequent germ cell tumors in the CNS. They typically occur along the midline, including areas like the suprasellar region, pineal gland, and basal ganglia. Tumors in the suprasellar region often present with visual and endocrine impairments. OBSERVATIONS: This article discusses the case of a 25-year-old patient with a tumor located in the suprasellar region, for whom an endoscopic endonasal approach was selected, with the preoperative objective of resection, owing to the suspicion of a craniopharyngioma. However, based on intraoperative findings, this diagnosis was excluded, prompting us to consider a germinoma, and the procedure was concluded with a biopsy. Postoperatively, the patient received chemoradiotherapy, resulting in a favorable resolution of the condition, improvement of symptoms, and a complete response observed on follow-up MRI. LESSONS: This case highlights three clinically actionable teaching points: arginine vasopressin deficiency (AVP-D) and anterior pituitary dysfunction in a young patient with a suprasellar mass should raise suspicion for germinoma, glucocorticoid replacement may unmask AVP-D by reversing cortisol deficiency-mediated antidiuresis, and the surgeon must be prepared to make real-time decisions based on intraoperative findings during endoscopic endonasal surgery. https://thejns.org/doi/10.3171/CASE2677.