The aim of this study is to establish patient-derived organoid (PDO) and tumor tissue cultures from breast cancer patients, in order to create personalized, accurate, and reliable preclinical models capable of providing information on the diverse biomolecular portraits of breast cancer. These models may also be used to predict the achievement of pathological complete response after neoadjuvant chemotherapy (NAC) treatment, study the biological, molecular, genetic, and microenvironmental characteristics of each tumor, and isolate tumor-derived extracellular vesicles from the PDOs and tissues and analyze them as potential biomarkers of response to NAC.

This study will recruit patients diagnosed with breast cancer who are candidates for neoadjuvant chemotherapy and subsequent surgery. Tumor tissue samples will be collected before and after treatment to establish patient-derived organoid cultures, which serve as personalized models of each patient's real tumor. Biomarkers released by the organoids (in particular those transported by extracellular vescicles) will be analyzed to identify predictors of therapeutic response. These biomarkers will be correlated with their expression in tumor tissue and subsequently validated in blood samples, collected pre, during and post treatment, as a non-invasive liquid biopsy approach. All data obtained will be analyzed by comparing patients who achieve a pathological complete response (pCR) with those who present residual disease after therapy (non-pCR).

Inclusion Criteria:

• Female subjects;
• Confirmed diagnosis of breast heteroplasia
• Age 1>= 8 years;
• Indication for neoadjuvant chemotherapy;
• Patients willing to follow the usual oncological follow-up;
• Patients with de novo metastatic disease (M+), receiving primary chemotherapy, if candidates for primary tumor biopsy;
• Subjects who agree to participate in the study by signing and dating the Informed Consent form.

Exclusion Criteria:

• Patients who have already undergone prior chemotherapy treatments;
• Patients without a proven cyto-histological diagnosis of breast carcinoma;
• Subjects affected by other solid tumors besides the breast lesion.

All patients consecutively referred to the Breast Unit of the IRCCS ICS Maugeri in Pavia and the Oncology Department of Sacco Hospital in Milan, who have breast neoplasm with an indication for neoadjuvant chemotherapy, will be included in the study.