CD44 and neoplasm: CD44 variant isoform exon 9 (CD44v9) was reported to be upregulated in several tumours, and it is thought to be involved in chemo‐resistance and the recurrence of tumours (Hirata et al., 2013; Horibe et al., 2018; Ishimoto et al., 2011; Ogihara et al., 2019; Wada et al., 2018; Wu et al., 2015; Yoshikawa et al., 2013).