Subsequent correlation analysis of the single stromal markers with patient- and histopathological tumor characteristics revealed a strong positive correlation between the stroma marker expression level and tumor stage for four of the five stroma markers (CD90, FAP p < 0.001; ASMA, PDGFRb p = 0.001 linear-by-linear association χ2-test) but not for PDGFRa (p = 0.141) (Supplementary Table 2; additional confirmation of this finding based on the raw scoring data is shown in Supplementary Fig. 3). Here, FAP is linked to neoplasm.