Mouse models play a crucial role in cancer drug development, with subcutaneous tumor models being the most prevalent in early drug discovery. However, orthotopic and metastatic tumor models are increasingly recognized for their ability to provide a more clinically relevant context for understanding target biology, tumor microenvironment interactions, and immune system responses. These models allow for a more comprehensive assessment of treatment efficacy and toxicity, enhancing the predictive value of preclinical studies. Orthotopic models involve implanting tumor cells or tissues at their anatomically correct site, while metastatic models simulate the spread of cancer cells to distant organs. Patient-derived xenografts (PDXs) and organoids are gaining popularity due to their ability to better recapitulate the human disease and improve the predictive value of preclinical studies. Humanized mouse models, which integrate human immune systems into immunodeficient backgrounds, further enhance the relevance of these models. Despite their advantages, orthotopic and metastatic models present challenges such as ethical considerations, complex surgical procedures, and the need for specialized imaging techniques. Non-invasive imaging methods like bioluminescence imaging (BLI) and ultrasound are widely used but have limitations, while advanced techniques like MRI, CT, and PET offer more detailed information but are less accessible. The use of orthotopic and metastatic models is expected to increase in preclinical cancer research, particularly with the development of disease-specific biobanks and advancements in imaging technologies. These models are essential for bridging the gap between preclinical research and clinical trials, improving the success rate of anticancer drugs and addressing the needs of both common and rare cancer types.Mouse models play a crucial role in cancer drug development, with subcutaneous tumor models being the most prevalent in early drug discovery. However, orthotopic and metastatic tumor models are increasingly recognized for their ability to provide a more clinically relevant context for understanding target biology, tumor microenvironment interactions, and immune system responses. These models allow for a more comprehensive assessment of treatment efficacy and toxicity, enhancing the predictive value of preclinical studies. Orthotopic models involve implanting tumor cells or tissues at their anatomically correct site, while metastatic models simulate the spread of cancer cells to distant organs. Patient-derived xenografts (PDXs) and organoids are gaining popularity due to their ability to better recapitulate the human disease and improve the predictive value of preclinical studies. Humanized mouse models, which integrate human immune systems into immunodeficient backgrounds, further enhance the relevance of these models. Despite their advantages, orthotopic and metastatic models present challenges such as ethical considerations, complex surgical procedures, and the need for specialized imaging techniques. Non-invasive imaging methods like bioluminescence imaging (BLI) and ultrasound are widely used but have limitations, while advanced techniques like MRI, CT, and PET offer more detailed information but are less accessible. The use of orthotopic and metastatic models is expected to increase in preclinical cancer research, particularly with the development of disease-specific biobanks and advancements in imaging technologies. These models are essential for bridging the gap between preclinical research and clinical trials, improving the success rate of anticancer drugs and addressing the needs of both common and rare cancer types.