Giant petroclival endodermal cyst with xanthogranulomatous changes.

Endodermal cyst is a rare developmental cyst of the CNS, such as a Rathke cleft and colloid cyst lined by columnar epithelium of presumed endodermal origin. Intracranial endodermal cysts are rare, and most are found in the posterior fossa. The authors report a case of petroclival endodermal cyst with extensive bone destruction. A 12-year-old boy presented with transient facial weakness and headache. Imaging revealed a 3 × 3 × 4-cm, partial rim, enhanced cystic lesion in the petroclival area that was isointense on T1-weighted imaging and hyperintense in T2-weighted imaging. The cyst wall was partially removed and the cyst was obliterated using a lateral approach. Histological examination revealed ciliated, simple-to-pseudostratified cuboidal epithelium with a basement membrane that was consistent with an endodermal cyst, with the rare finding of xanthogranulomatous changes.