We observed the levels of cfDNA were higher in TNBC patients compared to ER+ and HER2+ patients. We speculate that the lower levels of cfDNA in HR+ breast cancer compared with HER2+ and TNBC can be partly due to the lower cellular proliferation rates in this subtype. Our results are in agreement with studies by Magbanua et. Here, ESR1 is linked to breast carcinoma.