Also, this is particularly significant because HHLA2 expression may assist identification of a group of patients who might do poorly in spite of tyrosine kinase inhibitors (TKIs) for EGFR-mutated tumours (Janakiram et al., 2016; Cheng et al., 2017; Cheng et al., 2018). Here, HHLA2 is linked to neoplasm.