Cancer is one of the main causes of mortality. It is estimated that at some point in life one in three people will be affected by this disease. Although we have evidence of cancer as early as ancient times, we are still unable to provide effective and reliable treatments. In this short talk I would like to present the molecular basis of cancerogenesis. Firstly, I will focus on the genetic aspect of cancer and the role of mutations in specific biological pathways. Then I will present why it is very important to determine the status of variations in specific genes and how this modifies both the patient’s prognosis and the available therapeutic options. Finally, I will present one of our projects in the scope of personalized medicine in oncology.