Rathke cleft cyst with squamous metaplasia and activating mutations of mitogen-activated protein kinase signaling: illustrative case.

Background: Rathke cleft cysts (RCCs) are benign sellar/suprasellar lesions that result from mucin-secreting vestigial remnants within the pars intermedia of the pituitary gland. When symptomatic, they can present with retro-orbital headaches, visual field defects, and/or pituitary dysfunction.

Observations: A 35-year-old female presented with subacute retro-orbital headache, right ptosis, and blurred vision. Workup revealed panhypopituitarism with central hypothyroidism and adrenal insufficiency. Imaging demonstrated a sellar/suprasellar mass with subacute intralesional hemorrhage, which was thought to represent chronic pituitary apoplexy. The patient underwent an endoscopic endonasal approach in which the initial intraoperative frozen section suggested papillary craniopharyngioma. Subsequent specimens suggested RCC, thus presenting a surgical management conundrum. Hemihypophysectomy with lesionectomy was performed. Final histopathology demonstrated RCC with squamous metaplasia (RCC-SM), rupture, and hemorrhage. BRAF V600E was not detected. However, activating mutations in KRAS and MAP2K1 were identified.

Lessons: RCC can undergo SM and rupture, leading to a hemorrhagic-appearing cystic sellar/suprasellar mass associated with cranial nerve palsies and hypopituitarism that mimics pituitary apoplexy. Intraoperative frozen sections can be ambiguous due to overlapping histopathological features with craniopharyngioma, complicating surgical decision-making. The authors hypothesize that RCC-SM may represent a transitional state between RCC and craniopharyngioma. Neurosurgeons should be mindful of this transitional entity and be prepared to modify their surgical strategy accordingly. https://thejns.org/doi/10.3171/CASE24657.