S100B and melanoma: Laboratory tests are often not the first sign of metastasis and more definitive radiologic imaging is needed to definitively determine if distant metastases are present.48,83, -85 In a 2016 prospective cohort study that followed stage IIB, IIC and III melanoma patients for a median of 2.5 years, only 2.5% of patients had increased serum S100B or melanoma inhibitory activity protein as the first sign of metastasis.48