The Expression of Insulin-Like Growth Factor II Messenger RNA-Binding Protein 3 Upregulated in Intradural Extramedullary Schwannomas

INTRODUCTION: Tumor size is an important factor in determining the appropriate clinical management of intradural-extramedullary schwannoma. A tumor volume reduction may be achieved by conservative targeted therapy instead of invasive surgery if a molecular event related to tumor size is discovered. Insulin-like growth factor II messenger RNA-binding protein 3 (IMP3), an oncofetal tumor-associated antigen that is expected to be a target for immunotherapy, was focused on in this study. METHODS: The IMP3 status was assessed by immunohistochemistry in 64 samples of intradural-extramedullary schwannoma, and the correlation between IMP3 expression and tumor size was evaluated. RESULTS: Immunohistochemically, high IMP3 expression was observed in ～85% of schwannomas. The maximum tumor diameter of the high IMP3 expression group was significantly larger than that of the low IMP3 expression group (34.3 mm vs 18.5 mm, p=0.002). The receiver operating characteristic curve demonstrated that a maximum tumor diameter of 24 mm was a predictable factor for IMP3 expression (sensitivity, 0.7; 1−specificity, 0.2; area under the curve, 0.82). CONCLUSIONS: Upregulated IMP3 expression was associated with large tumor size, suggesting a possible therapeutic approach.