Expression of PGP 9.5 in granular cell nerve sheath tumors: an immunohistochemical study of six cases

Background: Protein gene product 9.5 (PGP 9.5) is expressed in brain at 20 to 50 times the levels detected in other organs. Immunohistochemical studie s reveal this protein is localized to both central and peripheral neurons. Recently, PGP 9.5 is reported to be a useful marker for cellular neurotheke omas. Herein we test whether PGP 9.5 is a new marker for granular cell nerv e sheath tumors. Material and Methods: An immunohistochemical analysis for PGP 9.5 expressio n was carried out on all cases with the diagnosis of granular cell nerve sh eath tumor seen over a 2-year period. In addition, we compared expression o f PCP 9.5 with other accepted markers for neuroectodermal tumors including anti-S-100 protein and NKI/C3 monoclonal antibodies. Results: Six granular cell nerve sheath tumors were diagnosed in over 80,00 0 dermatopathology specimens in the two-year period. These cases were all p ositive for PGP 9.5 as well as for S-100 protein and NK1/C3. Conclusion: These findings identify PGP 9.5 as a new immunohistochemical ma rker for use in the diagnosis of granular cell tumors, They also strengthen the histogenetic relationship between granular cell nerve sheath tumors an d tumors of Schwann cell or perineurial origin.