Rabbit Anti-Human IGF2BP3 polyclonal antibody for IHC-P. Insulin-like growth factor-II messenger RNA (mRNA) -binding protein-3 (IMP-3) , also known as K homology domain-containing protein overexpressed in cancer (KOC) and L523S, is a member of the insulin-like growth factor-II mRNA-binding protein family and is expressed during embryogenesis and in some malignancies. IMP-3 is expressed in malignant melanoma but not in benign nevi, even when dysplastic features are present; IMP-3 is expressed in a significantly higher proportion of melanomas than Spitz nevi; and IMP-3 is expressed in metastatic melanomas significantly more than in thin melanomas. IMP-3 appears to be involved in the progression of malignant melanoma and may play an important role in the regulation of the biologic behavior of this tumor.