Cancer is a disease characterised by the uncontrolled proliferation of cells, resulting from genetic mutations that disrupt the normal cell cycle. Unlike normal cells, cancer cells lose their ability to respond to signals regulating cell growth and division, and acquire the ability to divide indefinitely. These modified cells multiply uncontrollably, forming tumours that can invade and destroy surrounding tissue. In addition, cancer cells can break away from the original tumour and spread to other parts of the body, a process known as metastasis. Distinctive features of cancer cells include their ability to escape programmed cell death and to induce the formation of new blood vessels to ensure their supply of oxygen and nutrients. These characteristics make cancer a complex and multifactorial disease, requiring an in-depth understanding of its mechanisms in order to develop effective treatment strategies. In short, cancer results from the progressive transformation of normal cells into cancerous cells, which lose their control over growth and division and acquire the ability to metastasise, thereby threatening the health of the body.