Rosette forming glioneuronal tumor pineal gland and tectum: an intraoperative diagnosis on smear preparation.

We present an extremely rare case of newly described entity called rosette forming glioneuronal tumor (RGNT), involving the pineal gland, tectum, and the adjacent thalamus in a 22-year-old male. Interestingly, the ventricular system was not involved in this case. The tumor was diagnosed intraoperatively on smear preparation on cytomorphology. If sampled adequately, it is fairly easy to diagnose RGNT on smear preparation as it has a very distinctive cytomorphology of being composed of two population of cell. One of the components is pilocytic astrocytoma and the other is composed of small cells with scant cytoplasm, vesicular nuclei, arranged around neuropil-like material forming "neurocytic rosettes." To the best of our knowledge, this is the first case of RGNT in this rare location being diagnosed intraoperatively on smear preparation. 2009 Wiley-Liss, Inc.