Tumor formation, also known as oncogenesis or tumorigenesis, refers to the process by which normal cells transform into cancerous cells. This transformation occurs through a series of genetic mutations and alterations that disrupt the normal regulatory mechanisms controlling cell growth, division, and differentiation. Tumor formation can be initiated by various factors, such as exposure to carcinogens, genetic predispositions, chronic inflammation, or viral infections. These factors can lead to the accumulation of mutations in key genes involved in cell cycle regulation, DNA repair, and cell signaling pathways, ultimately driving the uncontrolled proliferation of cells and the development of a tumor. The study of tumor formation is a critical area of cancer research, as it provides insights into the underlying molecular mechanisms driving cancer development and progression. Understanding the process of tumorigenesis is essential for the identification of potential therapeutic targets and the development of novel strategies for cancer prevention and treatment.