The introduction of endoscopy, in conjunction with the technical development of endoscopy such as high definition and 3D, has had a significant impact on the field of endonasal transsphenoidal surgery. Currently, endoscopic surgery is applied for the resection of not only sellar tumors but also parasellar tumors such as anterior skull base tumors, intraorbital tumors, cavernous sinus tumors, infratemporal fossa tumors, clival tumors, and others. Endoscopic endonasal surgery is expected to be used more frequently in the near future. In this paper, based on our own experiences and after reviewing the recent publications, we summarize the indications for endoscopic surgery, focusing on pituitary tumors, craniopharyngiomas, and tuberculum sellae meningiomas. In pituitary tumor surgery, operative results by endoscopic and microscopic surgery are comparable for small tumors located in the sellar, while endoscopic surgery is superior to microscopic surgery for large tumors with extrasellar extension. Fully endoscopic surgery is more likely to be performed for giant pituitary adenoma cases for which craniotomy was previously preferred. However, tumors with significant anterior and lateral extension, multilobular suprasellar extension, and firm tumors can be limitations for endoscopic surgery. For craniopharyngiomas, retrochiasmatic tumors extending into the third ventricle can be good candidates for endoscopic surgery. In addition, the tumor-third ventricular relationship in craniopharyngiomas is another important factor to consider when deciding upon an indication for endoscopic surgery. The indication for an endoscopic approach for tuberculum sellae meningioma is limited to small anterior midline tumors for the purpose of decompression of the optic apparatus. In summary, although the efficacy of endoscopic surgery is well established, significant suprasellar and lateral extension and vascular encasement can be limitations for endoscopic surgery. For safe and effective endoscopic surgery, patient selection is important depending on the surgeons' operative techniques and experiences. Also, it is important to note that observation and manipulation are different, and it is necessary to acquire surgical techniques to prevent postoperative cerebrospinal fluid leaks.
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