“…In addition, the quantitative signatures would also be greatly affected by varied proportions of tumor epithelial cell in tumor tissues sampled from different tumor locations of the same patient (Cheng et al, 2017), partial RNA degradation during specimen storage and preparation (Chen et al, 2017), and amplification bias for minimum specimens even with about 15-25 cancer cells (Liu et al, 2017), which are common factors that can lead to failures in clinical applications. In contrast, the qualitative signatures based on relative expression orderings (REOs) of gene pairs within a sample are robust against the batch effects, different tumor locations, partial RNA degradation, and amplification bias (Zhao et al, 2016;Song et al, 2019), which could be directly applied to the sample at the individual level in clinical applications (Qi et al, 2016;Chen et al, 2017;Cheng et al, 2017;Liu et al, 2017;.…”