Expression of insulin-like growth factor II mRNA binding protein 3 (IMP3) in enchondroma and chondrosarcoma.

Atypical cartilaginous tumor and enchondroma are similar in histopathologic aspects. Although the clinical course, radiologic and pathologic examinations enable distinction in most cases, difficulties are still encountered by the pathologists. There is no known biomarker to help make a distinction between benign and malignant cartilaginous tumors. Insulin-like growth factor II mRNA binding protein (IMP3) is a member of an oncofetal family of proteins that is expressed in different human malignancies and rapidly emerging as a prognostic and diagnostic marker in surgical pathology. In this study, IMP3 expression was examined by immunohistochemistry in 36 enchondromas and 42 chondrosarcomas of different histologic grades. The results showed that all 36 cases of enchondroma were negative for IMP3, while it was overexpressed in 15 of 42 chondrosarcomas (36%) (P<0.01). Significant higher levels of IMP3 were detected in grade III chondrosarcomas (6 of 7; 85.7%) when compared to low-grade tumors (6 of 19; 31.5% in grade II and 3 of 16; 18.7% in Atypical Cartilaginous Tumor). We proved statistically significant difference in IMP3 expression between enchondromas and ACTs (P=0.025). Our study clearly demonstrated differentiation-dependent expression of IMP3 in chondrosarcoma, and suggests IMP3 as a novel marker for differentiating problematic cases of enchondroma from well-differentiated chondrosarcomas. To our knowledge, this study is the first study to clarify expression of IMP-3 in chondromas and chondrosarcomas.