C3 is an integral part of the complement system and was downregulated in all the patients in the study, indicating a good prognosis because the complement system is pathologically activated in the tumor microenvironment, which promotes tumorigenesis by regulating inflammation; stromal cell immunity; and the proliferation, epithelial-mesenchymal transition (EMT), migration and invasiveness of tumor cells (Zhang et al., 2019; Niculescu et al., 1992). Here, C3 is linked to neoplasm.