The initialevaluation and comparison of the 2A10 and 3C9 domainsare presented here as modified VH-Fc fusion proteins for PET-imaging.The performances of both anti-MSLN VH-Fc fusion proteins as PET-tracersare promising, demonstrating improved tumor accumulation and retentioncompared to an IgG1-based PET agent. Here, MSLN is linked to neoplasm.