Diagnosis and Surgical Management of Exophytic Suprasellar Pituitary Adenoma Extending Over the Diaphragma Sellae and Mimicking Craniopharyngioma: A Case Report

Abstract

Pituitary adenomas developing from the lateral surface of the pituitary gland are referred to as exophytic pituitary adenomas. When an exophytic pituitary adenoma extends into the suprasellar region, the tumor exhibits an atypical growth pattern that makes it difficult to distinguish it from craniopharyngiomas or other parasellar lesions on MRI. A 53-year-old woman who presented with general malaise and visual disturbances was diagnosed with a brain tumor. MRI showed a suprasellar tumor presenting as superior lobulation with reticular enhancement and partial calcification. Subsequently, endoscopic transsphenoidal surgery was performed on the patient. The suprasellar tumor was found to originate from the superior surface of the normal pituitary gland and it extended into the supra-diaphragm region. Subtotal tumor resection was achieved, and her clinical symptoms subsequently improved. Exophytic suprasellar pituitary adenomas (SPAs) are extremely rare and may be mistaken for ectopic SPAs in some cases. Contrast-enhanced fast imaging employing steady-state acquisition (CE-FIESTA) can clearly depict the connection between an exophytic SPA and the normal pituitary gland via a diaphragma sellae defect. During surgery, it was seen that the exophytic SPA and anterior lobe of the pituitary gland connected with each other directly. The tumor originated from the superior surface of the pituitary gland and extended into the supra-diaphragm region. These findings clearly confirmed the difference between exophytic SPAs and ectopic SPAs. In surgical management, an exophytic SPA needs careful consideration for resecting the tumor from encased surrounding structures without vascular and nerve injury. Ultrasonic aspiration devices may be useful for safely resecting the tumor from important structures due to tissue selection. Exophytic SPAs are distinguished from ectopic SPAs with respect to the direct connection between the tumor and the normal pituitary gland. These findings can be clearly depicted using CE-FIESTA and should be confirmed during surgery. Clinicians should be aware of the risk that exophytic SPA may extend into the supra-diaphragm region and of the difficulties of resecting the tumor encasing surrounding structures in the suprasellar region.

Keywords: craniopharyngioma; ectopic pituitary adenoma; endoscopic transsphenidal surgery; exophytic pituitary adenoma; fiesta; silent corticotroph adenoma; suprasellar pituitary adenoma; ultrasonic aspiration.

Figure 1. Preoperative MRI findings

Sagittal T1-weighted contrast and coronal T2-weighted magnetic resonance images showed a homogeneous intensity mass in the sella turcica and a lobulated reticular enhancement tumor (arrows) encasing optic nerves and cerebral arteries (arrowheads) in the suprasellar region (a, b). Dynamic enhanced MRI showed delayed enhancement of the suprasellar tumor (arrow) compared to that of the normal pituitary gland (arrowhead) (c). Sagittal CE-FIESTA MRI detected a diaphragm defect (arrow) and the tumor extending into the supra-diaphragm region (d) MRI: magnetic resonance imaging; CE-FIESTA: contrast-enhanced fast imaging employing steady-state acquisition

Figure 2. Intraoperative findings

The tumor was exposed via the extended endoscopic transsphenoidal approach. Comparison of diaphragm defects (arrows) detected on preoperative coronal CE-FIESTA MRI and surgery (A, B). The tumor arose from the superior surface of the pituitary gland and extended into the supra-diaphragm region through a diaphragm defect (C). The intrasellar pituitary gland had a normal appearance after tumor resection except for a connecting point (arrowhead) with the tumor, and an intact pituitary stalk was observed under the optic chiasm (D) ON: optic nerve; PG: pituitary gland; ACA: anterior cerebral artery; Acom: anterior communicating artery; PS: pituitary stalk; MRI: magnetic resonance imaging; CE-FIESTA: contrast-enhanced fast imaging employing steady-state acquisition

Figure 3. Postoperative MRI findings

Sagittal and coronal contrast-enhanced T1-weighted images showed that almost all suprasellar tumors were resected (arrows) except at the lateral region and around the laminar terminalis region (arrowheads) (A, B) MRI: magnetic resonance imaging

Figure 4. Histological examination findings

Histological examination showed diffusely labeled adenoma cells with deposits of hemosiderin (A). Immunohistochemical staining was focally positive for ACTH (B), and the MIB-1 labeling index was approximately 3% (C) ACTH: adrenocorticotropic hormone