Patient selection criteria included: Age equal or older than 45 years old; All cases of invasive carcinomas (in cases of lobular carcinomas only with MRI and confirmation); Patients who were 45–50 years old with a tumor size of 0–2 cm, 50–55 years old with a tumor size of < 2.5 cm, and those who were ≥ 55 years old with a tumor size of < 3 cm; Invasive tumors only with a negative margin; Negative nodal status (exception in patients with micrometastasis); A positive estrogen receptor status. This evidence concerns the gene ESR1 and breast lobular carcinoma.