The investigators will select patients with a diagnosis of breast cancer who undergo breast surgery. Patients will be asked informed consent for the use of a small (0,2-1 cm3) sample of the excised breast tumour and the collection of a blood sample (6ml)for whole-exome sequencing (WES) to compare the genetic profile of the patients with the organoids and the patient biopsy. The patients will not undergo any additional treatment or procedure in addition to the planned routine procedure for the surgical resection of their primary breast tumour.
Patient will undergo standard diagnostic procedures and treatment according to the Dutch breast cancer surgery guidelines. After surgery, the pathologist will provide -after pathological diagnosis- rest (tumour) tissue from the resection to the lab. This material will then be used to develop breast cancer organoids. As part of the routine surgical procedure, 6 ml of blood will be collected. Participation in this study does not lead to additional actions other than reading the patient information and signing the informed consent. Therefore, participation does not change the patient's treatment or outcome.