Primary peripheral PNET/Ewing's sarcoma arising in the meninges, confirmed by the presence of the rare translocation t(21;22) (q22;q12)

Peripheral primitive neuroectodermal tumor/Ewing's sarcoma (ES) (pPNET/ES) of intracranial origin are very rare. These tumors are characterized by specific translocations involving a gene on chromosome 22q12, the most common being t(11;22) (q24;q12). We report a case of 37-year-old man with pPNET/ES arising in the meninges and bearing the rare translocation t(21;22) (q22;q12). The tumor was composed of sheets and nests of monotonous small cells with round to oval nuclei, finely dispersed chromatin, small nucleolus and scant cytoplasm. We discuss the importance of the differential diagnosis with central primitive neuroectodermal tumors (cPNET). © 2011 Japanese Society of Neuropathology.