Normal Pituitary Gland Showing an Intratumoral Septal Structure in a Nonfunctioning Pituitary Neuroendocrine Tumor: Illustrative Case.

Normal pituitary glands are usually found to be present in the periphery of tumors. Normal pituitary gland showing an intratumoral septal structure has not been sufficiently discussed. A 73-year-old man presented with a visual field disorder. Endocrinologically, his basal luteinizing hormone and follicle-stimulating hormone levels were elevated. Gadolinium-enhanced T1-weighted magnetic resonance imaging revealed a sellar tumor. A well-enhanced normal pituitary gland was found with a septum-like shape slightly to the right of the tumor in the coronal section, and the tumor seemed to have grown independently on the cavernous sinus and sellar sides. Endoscopic transsphenoidal surgery was performed. After removal of the main tumor on the left side, the normal pituitary gland wall was confirmed to be intact. We observed a crack-like hole in the septum-like structure of the pituitary gland. We removed the tumor on the right side using this hole in the septum-like normal pituitary gland. This case was thought to have arisen because the adenoma perforated the normal pituitary gland during its development and then progressed outward, which is different from a double pituitary adenoma. In such cases, we should locate the hole in the septum-like structure of the normal pituitary gland and remove the tumor laterally progressing from this hole during endoscopic surgery.