Intraventricular dysembryoplastic neuroepithelial tumor in a pediatric patient: is it the most common extracortical location for DNT?

Dysembryoplastic neuroepithelial tumor (DNT) is commonly located in the supratentorial cortex. Extracortical localization of DNT is extremely rare. A 15-year-old female presented with loss of consciousness after head trauma. MRI demonstrated hydrocephalus secondary to a small non-enhancing T1 hypointense and T2 hyperintense mass lesion in the foramen of Monro; with radiologic impression of low-grade astrocytoma or colloid cyst. Tumor was gross totally resected. Histologic examination showed partly microcystic architecture with oligodendroglia-like neurocytic cells, glioneuronal element, and floating neurons, with synaptophysin reactivity mainly in cell processes, consistent with DNT. Focal subependymoma-like pattern was noted. The low tumor cellularity and morphologic pattern did not support a central neurocytoma. Patient was asymptomatic and was radiologically stable 9 months post-surgery. Literature review of previously reported supratentorial extracortical DNT cases demonstrate that 24 of 25 cases involved the ventricular system (as in our case) of which eight additionally involved periventricular deep gray or white matter. None of the cases recurred following surgery. Clinico-pathologically, extracortical DNTs were similar to the cerebral cortical simple DNTs and differed only in their presentation related to their location. The novel aspects of this report are the radiologic resemblance of DNT to colloid cyst and focal subependymoma-like pattern on histology. Importantly, intra-/periventricular region appears to be the most common extracortical location of cerebral DNT with a 100% disease-free survival reported in the literature.