Early Breast Cancer (EBC)

The goal of this observational study is to explore the utility of analytical techniques that enable the study of small amounts of tumor-derived material circulating in the blood, such as fragments of circulating tumor DNA (also known as ctDNA), cells, or other particles. This type of sample is generally referred to as a liquid biopsy, and its analysis is a minimally invasive test, as it only requires the collection of blood samples. The study includes women and men with early-stage breast cancer (EBC) who are about to start neoadjuvant treatment (treatment given before surgery). The main questions it aims to answer are: * Can liquid biopsy analyses (ctDNA) provide additional information about the type of tumor before treatment starts? * Can these analyses help to detect early whether the tumor is responding to treatment? * Can these tests identify if any cancer remains after neoadjuvant treatment or after surgery? * Is this information related to the risk of the cancer coming back? * Can these analyses, when performed during follow-up, help detect cancer recurrence earlier? Participants will: * Continue receiving standard medical care for their breast cancer, including neoadjuvant therapy and surgery. * Provide blood samples at different time points during treatment and follow-up. * Provide residual tumor samples from the routine clinical care.