Introduction In the 19th century, Rudolf Virchow observed the presence of leukocytes within tumor tissues. This observation created the first possible link between inflammation and cancer. Over the past two decades our understanding of inflammation and cancer has supported Virchow's observations (1). Up to 15% of global cancers have been associated with infections, and there is strong evidence that chronic inflammation and autoimmune reactions can increase cancer risk (2). Inflammation can act as an initiator of cancer, as local inflammation enriches tissues with oxygen, nitrogen, and free radicals that kill pathogens, and can directly cause DNA damage and DNA mutations (3). The immune system has the ability to mediate the repair of damaged tissues, releasing cytokines, chemokines and growth factors, these agents can directly or indirectly stimulate the proliferation of tumor cells (4). Inflammatory cells also appear to play a crucial role in vessel formation and can provide tumors with necessary components and play an important role in metastasis (3). However, the inflammatory process can also contribute to the elimination of tumor cells. Tumor cells produce antigens that can be recognized both by specific immunity and by innate immunity through natural killer (NK) cells (5). These statements explain the extraordinary importance of inflammation and how it can act as a double-edged sword: under specific stimulation it can produce factors and free radicals capable of directly destroying tumor cells. However, it appears that some tumors can use inflammatory responses to their advantage to grow and move throughout the body. Purpose and methods It is clear that we need to increase our knowledge about inflammation... half of the article... ...Production procedures do not survive and only a small part can survive, so to produce transgenic mice a large number of animals (20). Conclusion Inflammation plays a multifactorial role in cancer development. The inflammatory process can initiate, promote or inhibit tumor progression. In vitro studies cannot provide a complete picture of the involvement of inflammation in cancer, unlike in vivo tumor models that provide the basis for screening new targets that could improve cancer therapeutic strategies. Although in vivo transgenic tumor models are widely used, they present some economic and ethical challenges. Furthermore, tumor-bearing mice are not the best model for studying the antitumor activity of the immune system because the inflammatory infiltrate is far less massive in mouse tumors than in human ones. (2).