NR4A1 and breast cancer: When studying ctDNA levels in pretreatment plasma samples, they observed that HER2-positive patients showed median ctDNA amount of 0.81 copies/mL (range 0–5.4), intermediate between triple negative BC (TNBC) with the highest levels (median 4.96 copies/mL, range 0–17.0) and hormone-receptor (HR)-positive tumours with the lowest ctDNA levels (median 0 copies/mL, range 0–4.4) [28].