Soluble forms of proteins involved in tumor-cell proliferation (e.g. soluble stem-cell factor receptor [sKIT]) or tumor angiogenesis (such as VEGF-A, VEGF-C, soluble VEGFR-2 [sVEGFR-2], and soluble VEGFR-3 [sVEGFR-3]) can be rapidly and readily measured in serum or plasma samples by highly specific enzyme-linked immunosorbant assays (ELISAs). Here, FLT4 is linked to neoplasm.