Oncology is the branch of medicine specializing in the study of the nature of tumors, both benign and malignant, although the focus is on the latter, i.e. cancer. This clinical specialty is responsible for developing and applying techniques that are useful for the prevention, early diagnosis and treatment of cancer, which continues to represent one of the main causes of death in the world. Research in this clinical field is of vital importance, as we are still searching for a cure for this disease. In this section we will discuss the nature of cancer, studying both the most common and less frequent cancers, as well as the latest advances in detection techniques and therapies to treat them.