ESR1 and neoplasm: Compared to low Treg tumours, high Treg tumours also significantly correlated with negative ER status (73/262 (28%) and 81/216 (38%) ER negative respectively, P = 0.025), positive HER2 status (7/245 (3%) and 20/206 (10%) HER2 positive respectively, P = 0.002) and positive CXCL12 expression (74/125 (59%) and 83/110 (75%), P = 0.008).