Women in our study population were on average 62 years old with predominantly low-risk pathological features and good general health status (median Karnofsky index = 100%), tumor ≤ 2 cm (69.6%), low to intermediate grade (78.1%), negative axillary nodes (pN0; 73.4%), and positive estrogen receptor (92.2%). Here, ESR1 is linked to neoplasm.