Reply to letter to the editor: hybrid peripheral nerve sheath tumor

Abstract

We would like to thank Dr. Teresa Pusiol and her colleagues for their interest in our paper and for their valuable comments. We agree with their comments that hybrid peripheral nerve sheath tumor has been previously reported in extradigital sites. The normal peripheral nerve sheath consists of Schwann cells, fi broblasts, and perineurial cells, and benign peripheral nerve sheath tumor including schwannoma, neurofi broma, and perineurioma is generally composed of these cells. Previous ultrastructural studies have elucidated that peripheral nerve sheath tumors contain these cells in various proportions. Recently, peripheral nerve sheath tumors with discrete areas of more than one histological type have been described, and these tumors have been designated as hybrid peripheral nerve sheath tumor (HPNST). HPNST consisting of two components is pathologically subdivided into schwannoma-neurofi broma, schwannoma-perineurioma, and neurofi broma-perineurioma. Furthermore, we believe that HPNST consisting of all three components with a discrete area, namely schwannoma-neurofi broma-perineurioma, actually exists, although this tumor may be extremely rare.