In vivo tumor models like solid and ascites tumors are essential for studying cancer biology and therapeutic responses. Solid tumor models mimic real tumor growth and angiogenesis, while ascites models, often used with Ehrlich Ascites Carcinoma (EAC), simulate peritoneal cancer spread. These models are instrumental in evaluating anti-cancer drug efficacy, dosing strategies, and toxicity in a living system, offering translational insights for human treatments.