After correction for multiple testing, serum concentrations of EGF, CAL, MMP-1, MMP-7, MMP-9, CEA and CYFRA 21.1 were significantly elevated in LC compared to controls (Mann-Whitney U test, P = 0.001 for EGF, CAL, MMP-9, CEA and CYFRA 21.1; P = 0.047 for MMP-1 and P = 0.013 for MMP-7), while sCD26 levels were notably lower in malignancy relative to controls (Mann-Whitney U test, P = 0.001). Here, MMP9 is linked to cancer.