ABSTRACT
<p><b>OBJECTIVE</b>To study the significance of P504s in differential diagnosis between solid pseudopapillary tumor of the pancreas (SPTP) and pancreatic neuroendocrine tumors (PanNET).</p><p><b>METHODS</b>Forty-three patients with SPTP and 41 patients with PanNET encountered during the period from 2007 to 2014 were recruited. Immunohistochemical study for vimentin, CD10, chromogranin A, synaptophysin, beta-catenin, CD99 and P504s in SPTP and PanNET was performed. The diagnostic value of P504s in differentiating SPTP from PanNET was analyzed.</p><p><b>RESULTS</b>Immunohistochemical study showed that vimentin, CD10, chromogranin A, synaptophysin and CD99 were expressed both in SPTP and PanNET. All cases of SPTP showed granular cytoplasmic expression of P504s, whereas those of PanNET were negative.</p><p><b>CONCLUSION</b>P504s is a sensitive and useful marker for SPTP and can be used in the distinction between SPTP and PanNET.</p>