Kim et al. (2020) found that CTSB was a promising prognostic marker of thyroid cancer due to its function of enhancing the migration capacity of cancer cells. It was also identified that CTSB played a cancer-promoting role in endometrial and cervical cancers (Wu et al., 2012; Bao et al., 2013). As for CTSL, Zhang et al. (2014) reported that the upregulated CTSL was a biomarker of invasion and metastasis in ovarian cancer. Here, CTSL is linked to thyroid cancer.