CD99 is one of the most important immunohistochemical markers for the diagnosis of PNET.[12] Dong et al[13] summarized 20 PNET cases reported in the past 2 decades and found that there were 9 cases with the overall survival of 23.6 months (from 5 to 54 months), while there were still 9 cases alive with mean survival time over 17.2 months. The gene discussed is CD99; the disease is primitive neuroectodermal tumor.