A Clival Mass Posing a Diagnostic Challenge: Pituitary Adenoma With Rathke Cleft Cyst Mimicking Chordoma

Ectopic or extrasellar pituitary adenomas (PAs) in the clival region are extremely rare and can mimic aggressive skull base tumors on imaging, posing a diagnostic challenge. We present the case of a 54-year-old woman with a six-month history of severe, pulsatile headaches, without visual, endocrine, or neurological deficits. Laboratory evaluation revealed mild metabolic abnormalities. Imaging demonstrated a large, destructive clival mass with heterogeneous enhancement, bone erosion, lateral extension into the cavernous sinus and Meckel's cave, and encasement of the left internal carotid artery, strongly suggestive of a clival chordoma. The patient underwent staged surgical resection, including endoscopic endonasal and left orbitozygomatic approaches. Intraoperative frozen section suggested pituitary tissue, and final histopathology confirmed a PA associated with a Rathke cleft cyst. This case highlights the diagnostic challenges of clival lesions: radiologic aggressiveness may not reflect the underlying pathology, and clinical symptoms may be minimal despite extensive tumor burden. Definitive diagnosis requires integration of imaging, surgical findings, and histopathology. Multidisciplinary collaboration is essential to guide appropriate management, avoid misclassification, and optimize outcomes.