Pathophysiology
Clinical meaning
Breast cancer develops when cells in the breast tissue grow uncontrollably and form a malignant tumor. Most breast cancers begin in the cells lining the milk ducts (ductal carcinoma) or the lobules that produce milk (lobular carcinoma). These abnormal cells accumulate genetic mutations that allow them to divide without normal regulatory control, invade surrounding tissues, and potentially spread (metastasize) to lymph nodes and distant organs. Breast cancer can be classified by its receptor status - whether the cancer cells have receptors for estrogen (ER), progesterone (PR), or the HER2 protein - which determines treatment options. Early detection through screening and self-examination significantly improves outcomes.