A Pars Intermedia Macroadenoma Supporting the Origin of Silent Corticotroph Adenomas

Introduction: Silent corticotroph adenomas (SCAs) are the only pituitary adenomas thought to originate from the pars intermedia. This case report presents a novel/rare magnetic resonance imaging (MRI) finding demonstrating displacement of the anterior and posterior pituitary glands by a multimicrocystic corticotroph macroadenoma, supporting the hypothesis that silent corticotroph adenomas originate from the pars intermedia and should be considered in the differential diagnosis for pars intermedia lesions. Case: A 55-year-old man presented with an episode of confusion and blurred vision. MRI demonstrated separation of the anterior and posterior glands by a solid-cystic lesion located within the pars intermedia with superior displacement of the optic chiasm ([ Fig. 1 ]). Endocrinologic evaluation, including a dexamethasone suppression test, was unremarkable with no signs of suppression. The differential diagnosis was a pars intermedia pituitary adenoma versus a craniopharyngioma. An endoscopic endonasal transsphenoidal approach was performed with intent to explore the pars intermedia adenoma via a transsellar approach, with further removal of the tuberculum sella in case pathology revealed a craniopharyngioma. The tumor was confirmed to be a pituitary adenoma and was dissected readily from the gland ([ Fig. 1 ]). Discussion: The origin of SCAs, whether from corticotrophic cells of the pars intermedia or pars distalis, remains controversial. This case demonstrated a mass positioned in the pars intermedia, with distinctly preserved and displaced the anterior and posterior pituitary lobes supporting the theory that SCAs arise from the pars intermedia. As part of the differential diagnosis of pars intermedia lesions, Rathke's cleft cysts (RCC), craniopharyngiomas, and corticotroph adenomas should be considered. Typically, craniopharyngiomas extends beyond the sella, often involving the neurohypophysis, and appear hypointense on T1 and hyperintense on T2 imaging, and exhibit a solid-cystic consistency. In contrast, RCCs often demonstrate T1 and T2 hyper- and hypointensity, respectively. The tumor's multimicrocystic appearance on MRI is highly suggestive of a corticotroph adenoma. Conclusion: The pars intermedia are hypothesized to be the origin of silent corticotroph adenomas. This case report emphasizes the importance of including SCA on the differential diagnosis of a pars intermedia lesion. The case also highlights the importance of preoperative screening for subclinical hypercortisolism for tumors thought to be arising from this location as it may help determine whether postoperative biochemical assessment is required to determine whether remission has been achieved. The case also illustrates the challenge of resecting tumors originating from the pars intermedia without injury to the anterior gland. Publication History Article published online: 01 February 2023 © 2023. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany