Breast cancer is the most common malignancy and the leading cause of cancer related death in women of the western world. For most women, increasing age is the primary risk factor for breast... Show more Breast cancer is the most common malignancy and the leading cause of cancer related death in women of the western world. For most women, increasing age is the primary risk factor for breast cancer. Therefore, the number of breast cancer patients is expected to further increase in the coming years. The work presented in this thesis is part of the collaborative FOCUS project, seeking insight into breast cancer disease (in the elderly), aiming to define normal tissue, breast cancer, and therapeutic sensitivity differences in observational, population-based cohorts consisting of elderly breast cancer patients. Topics discussed in this thesis are differences and clinical value of molecular differentiation, immune evasion, proliferative and apoptotic signaling; but also the predictive value of IGF1R and HER2 expression on the breast tumors. Last but not least, we discuss the effects of aging on tumorgenesis and the road to precision medicine. Only when all medical specialties bound to the care and cure of older cancer patients join forces, known as a multidisciplinary oncogeriatric battlefront, treatment goals, and implementation hereof will be achieved. Show less