Endodermal cyst: rare intraaxial brainstem location. Illustrative cases

Abstract

Background: This report detailed an extremely rare location of an endodermal cyst. Such location of the tumor can pose radiological confusion and a therapeutic dilemma. However, when identified, it can be a pleasant surprise for the surgeon and provide the possibility of a symptom-free long life for the patient.

Observations: This report discussed two young patients who presented with relatively short-duration reports of ataxia and diplopia. Investigations revealed intraaxial brainstem lesion. During surgery, thick, pus-like fluid was evacuated and part of a wall was resected. Histology revealed that the lesion was an endodermal cyst. Both patients are well and are lesion- and symptom-free for 24 and 72 months.

Lessons: Endodermal cysts are some of the few long-standing and benign intraaxial brainstem lesions.

Keywords: brainstem; endodermal cyst; neurenteric cyst.

FIG. 1.

Images of a 21-year-old male patient. A: T1-weighted sagittal MRI showing the hypointense lesion with areas of hyperintensity in the pons. A small connection can be seen extending from the ventral aspect of the pons to the clivus. B: T2-weighted axial image showing the hyperintense cystic lesion. C: Contrast-enhanced coronal image showing ill-defined enhancement. D: Postoperative sagittal contrast-enhanced image showing excision of the lesion. E: Postoperative T2-weighted image. F: Postoperative axial MRI showing excision of the endodermal cyst. G: Original magnification ×400. Hematoxylin and eosin stain showing endodermal cyst wall lined by pseudostratified ciliated columnar epithelium.

FIG. 2.

Images of a 14-year-old female patient. A: T1-weighted sagittal image showing the hypointense pontine lesion with central hyperintensity extending up to the ventral border of the pons. B: T1-weighted contrast-enhanced axial image showing no contrast enhancement. C: T2-weighted axial image showing the hyperintense lesion. D: Postoperative contrast-enhanced axial image showing resection of the tumor. E: Postoperative sagittal image showing resection of the endodermal cyst.