Challenges in intraoperative differentiation of craniopharyngioma and Rathke cleft cyst on endoscopic visualization

Craniopharyngiomas are epithelial tumors derived from the remnants of the Rathke pouch, while Rathke cleft cysts (RCC) are benign cystic lesions originating from the Rathke pouch itself [1]. Rathke cleft cysts comprise 10-15% of the hypophyseal tumors, while craniopharyngiomas are relatively rare, comprising only 2-5% of intracranial tumors [2]. Both located in the sellar and parasellar regions and share clinical symptoms including headache, visual disturbances, and endocrine dysfunction [3]. Rathke cleft cysts and craniopharyngiomas can be challenging to differentiate preoperatively, distinguishing between them is crucial due to the significant differences in their management and surgical decision-making. However, once the surgical decision is made, their intraoperative appearance on the endoscopic view often differs. In such cases, the macroscopic appearance can play a key role in determining the extent of surgical aggressiveness. Even though, in both cases maximal safe resection is advisable, in craniopharyngioma a difference with RCC extent of resection is proportional to progression free survival [4].

The authors present their experience with a 40-year-old female patient with no relevant medical background, presenting frequent headaches for approximately 3 months, neuro-ophthalmological and endocrinological evaluation were within the normal limits. Brain MRI showed an enhanced sellar mass, radiological chiasmatic compression. Differential diagnosis was for craniopharyngioma or RCC. An endoscopic endonasal transsphenoidal surgery (EETS) was performed. Intraoperative features all pointed towards craniopharyngioma, typical "oil like cyst" with solid components such as cholesterol crystals and an adhered capsule to the surrounding structures. Complete resection was achieved, post operative CT and MRI were reassuring of a positive outcome. The pathological report unexpectedly identified the lesion as a Rathke cleft cyst. On H&E stained microscopic slides, a cyst lined by stratified squamous epithelium and superficial goblet cells was observed. Which is consistent with squamous metaplasia of Rathke's cleft cyst. There was also a lack of stellate reticulum, wet keratin, and calcifications; features characteristic of Adamantinomatous craniopharyngioma, further ruling out this diagnosis. Without papillary structures and in the absence of BRAF V600E mutation, as confirmed by testing, papillary craniopharyngioma was also ruled out.

Rathke cleft cysts and craniopharyngiomas have overlapping clinical and radiological features, making it challenging to differentiate between the two preoperatively. Intraoperatively commonly in the endoscope screen the difference of both pathologies is clearer and it could influence the surgeon's intraoperative aggressiveness towards the resection. This case exemplifies how intraoperative diagnosis by the surgeon can differ from the final diagnosis. In this case, although the pathology report was not consistent with the surgeon's intraoperative diagnosis, the patient still got appropriate treatment and an excellent outcome.