Abstract. This paper explores the pathophysiological mechanisms underlying tumor development in detail. It focuses on the cellular and molecular changes that lead to tumor formation, such as genetic mutations, disruption of apoptosis, uncontrolled activation of growth factors, and the weakening of immune surveillance. The study provides a comprehensive overview of how tumor cells create a supportive microenvironment, including the stimulation of angiogenesis, evasion of the immune system, and the process of metastasis to distant tissues. Additionally, the paper examines the metabolic adaptations of tumor cells, their interaction with the surrounding tissues, and how these factors contribute to tumor progression.