CD204, also known as macrophage scavenger receptor 1 (MSR1) or scavenger receptor A (SR-A), is a class A scavenger receptor primarily expressed on macrophages and dendritic cells. It functions as a pattern recognition receptor that binds to a wide range of polyanionic ligands, such as modified lipid proteins and pathogen-derived molecules. CD204 plays roles in lipid metabolism, atherogenesis, and various metabolic processes. It is also involved in innate defense against pathogens and has been implicated in several diseases, including Alzheimer's disease. In cancer, CD204 is a specific marker of tumor-associated macrophages (TAMs) and is associated with poor prognosis in glioma and breast cancer. Additionally, CD204+ monocytes and macrophages can suppress proinflammatory cytokine production and protect mice from septic shock.