Breast cancer is the most diagnosed tumour in women and remains a leading cause of cancer-related death worldwide. When the tumour reaches significant dimensions, mastectomy becomes necessary. This surgical procedure involves the removal of the breast tissue. Whenever possible, reconstructive procedures are performed to restore the shape and symmetry of the thoracic profile. Among the available techniques, implant-based breast reconstruction represents one of the most commonly adopted solutions. The present work aims to develop a digital 3D system designed to support surgeons during preoperative planning. The workflow combines 3D modelling, breast segmentation, and volumetric analysis to provide reliable information. The project was carried out in collaboration with the Breast Unit of Cottolengo Hospital in Turin, which provided access to a dataset based on real clinical cases.