Progression of Atypical Extraventricular Neurocytoma to Anaplastic Ganglioglioma

We report a childhood case of thalamic atypical extraventricular neurocytoma that progressed to highly anaplastic ganglioglioma (GG) after eight years of dormancy following subtotal resection and chemotherapy. The neurocytoma displayed immunoreactivity only for synaptophysin, beta-catenin, S-100 and CD56. The GG acquired strong immunoreactivity for chromogranin, glial fibrillary acidic protein, neuron specific enolase and p53 and showed a very high proliferation rate approaching 50% in some areas. Tumor transformation was associated with overexpression of components of the sonic hedgehog (Shh) and Wnt developmental signaling pathways, which are known to regulate tumor-initiating cells in malignant brain neoplasms.