Treatment strategy for infantile neuroblastoma with MYCN amplification or gain based on MYCN immunohistochemistry: a report of two cases

Abstract

Abstract Background MYCN-amplified neuroblastoma almost always expresses the MYCN protein. MYCN amplification is one of the crucial risk factors for a poor prognosis. However, there are scattered cases in which MYCN protein expression is absent despite MYCN amplification, making it difficult to evaluate the prognostic importance of MYCN amplification. Recently, the usefulness of MYCN protein expression in the histological diagnosis of neuroblastoma has been reported, but there are only a few cases of treatment intensity reduction based on negative protein expression despite MYCN amplification. Case presentation: Herein, we report two cases of infantile neuroblastoma—a 3-month-old girl and 10-month-old boy with stage 4S and 2B neuroblastoma, respectively—with MYCN amplification or gain without MYCN expression. The 3-month-old girl with stage 4S disease was initially treated with one course of chemotherapy before biopsy due to hepatomegaly causing abdominal compartment syndrome. MYCN amplification was evident, but MYCN expression was negative; therefore, treatment intensity was reduced and autologous stem cell transplantation was not performed. The 10-month-old boy with stage 2B showed MYCN gain on initial biopsy, but was negative for MYCN expression. Therefore, he was treated with conventional chemotherapy and surgery. Both patients were treated with conventional chemotherapy and 13-cis-retinoic acid without autologous stem cell transplantation. They remained disease free for 10 and 7 years post-resection, respectively. These two cases led us to speculate that MYCN protein expression more closely reflects the nature of a tumor than MYCN amplification or gain. Conclusions Nevertheless, chemotherapy could be optimized based on histological features and MYCN expression rather than MYCN amplification or gain. It is expected that MYCN expression will be considered as a factor in determining treatment intensity for MYCN-amplified or -gain tumors.