Dysplastic ganglioneurocytoma with increased glucose metabolism: a heterotopia with unique histopathology.

A 1 year and 7 month old boy was incidentally found to have an intracranial mass lesion at the frontal base. The mass was 45 x 54 x 47 mm in size, contained a calcification, a few small cysts, and extended downward to the sphenoid sinus and upper pharynx. The signal intensity of the lesion on magnetic resonance imaging was iso-high on T1-weighted images, and slightly high on T2-weighted images, and it did not enhance with gadolinium injection. Although there was no obvious mass effect, 18F-fluorode-oxyglucose positron-emission tomography demonstrated increased uptake, and a surgical resection was performed suspecting a neoplastic lesion. Histologically, the lesion consisted of small to large anomalous neurons and glial cells but lacked normal cortical architecture. Cellularity was high in some portion with MIB-1 labeling index of 2%, but there was no cellular atypia suggestive of neoplasm. Therefore, this lesion was considered to be a dysplasia that does not fit into the previously described entity. We suggest this lesion would be better described as dysplastic ganglioneurocytoma.