Mucinous adenocarcinoma arising from a residual supratentorial neurenteric cyst and expressing mutated KRAS: a case report.

Malignant transformation of intracranial neurenteric cysts (NCs) has been reported in only 7 cases, but the molecular characteristics leading to malignant transformation remain unclear. A 61-year-old woman presented with headache and dizziness. Imaging revealed a 10-cm, extra-axial cystic mass in both middle fossae. A partial resection was performed, and the residual mass size gradually decreased. She had repeated ventriculoperitoneal shunts to relieve symptoms of hydrocephalus. Eight years later, follow-up images revealed marked enlargement of the mass and a newly developed lesion. After a second partial resection, a mucinous adenocarcinoma infiltrating the brain was identified. Transitions from benign-looking cuboidal cells to dysplastic cells were observed. A KRAS mutation, which might be associated with malignant NC transformation and was not present in the initial specimen, was identified in the adenocarcinoma. In conclusion, KRAS-mutant mucinous adenocarcinoma may arise in a longstanding residual NC after partial resection.