Malignant Transformation of a Supratentorial Neurenteric Cyst: A Case Report and Literature Review.

Neurenteric cysts (NECs) are congenital lesions of endodermal origin that are uncommon, and malignant transformation is extremely rare. They are predominantly found in the spinal subdural space. We report a case of a 50-year-old female with a known history of hypothyroidism, presenting with a nine-month history of severe occipital headache, neck pain, and rigidity, accompanied by a notable unintentional weight loss of 20 kg. Neurological examination was unremarkable. Imaging studies revealed a complex multilobulated cystic lesion involving the velum interpositum and the trigone of the left lateral ventricle. Diffuse craniocervical spinal cord leptomeningeal enhancement was identified. Lumbar puncture confirmed rare, atypical epithelial cells. Gross total resection of the tumor was done through a parietal craniotomy. Histopathological examination revealed transitional features of a neurenteric cyst from benign to malignant, supported by morphological and immunohistochemical findings. Neurenteric cysts, though rare in supratentorial or infratentorial locations, should be included in the differential diagnosis of intracranial cysts. The presence of benign epithelium and dysplastic epithelium with malignant features, together with a high proliferation index, indicates malignant transformation of the neurenteric cyst. To the best of our knowledge, this is the fourth case reported so far that is distinct regarding location, with the velum interpositum and the trigone of the left lateral ventricle rarely being reported sites.