IFNG and breast cancer: Our study is significant because (1) it identified new markers and refined classification (Fig 4D) that will help in isolation of γδ T-cell subtypes for further functional characterization; (2) it identified previously hidden gene expression heterogeneity in both the TRDV2low and TRDV2high subtypes and (3) it identified gene signature and a marker of a IFNG+ TRDV2low subtype in breast tumours that is associated with better survival of breast cancer patients.