The article reviews the identification and functional characterization of novel tumor-associated macrophage (TAM) subpopulations in solid tumors using single-cell RNA sequencing (scRNA-seq). Four distinct TAM subpopulations—*FCN1*+, *SPP1*+, *C1Q*+, and *CCL18*+—are identified based on core gene signatures. *FCN1*+ TAMs are associated with inflammation, *SPP1*+ TAMs with metastasis, angiogenesis, and cancer cell stem cell activation, *C1Q*+ TAMs with immune regulation and suppression, and *CCL18*+ TAMs with terminal immunosuppression and enhanced tumor metastasis. These subpopulations exhibit high phenotypic plasticity and heterogeneity, and their functions are influenced by tumor microenvironment factors. The review also discusses the potential clinical implications of these subpopulations as targets for cancer immunotherapy, highlighting the need for further research to clarify their exact functions and develop targeted therapies.The article reviews the identification and functional characterization of novel tumor-associated macrophage (TAM) subpopulations in solid tumors using single-cell RNA sequencing (scRNA-seq). Four distinct TAM subpopulations—*FCN1*+, *SPP1*+, *C1Q*+, and *CCL18*+—are identified based on core gene signatures. *FCN1*+ TAMs are associated with inflammation, *SPP1*+ TAMs with metastasis, angiogenesis, and cancer cell stem cell activation, *C1Q*+ TAMs with immune regulation and suppression, and *CCL18*+ TAMs with terminal immunosuppression and enhanced tumor metastasis. These subpopulations exhibit high phenotypic plasticity and heterogeneity, and their functions are influenced by tumor microenvironment factors. The review also discusses the potential clinical implications of these subpopulations as targets for cancer immunotherapy, highlighting the need for further research to clarify their exact functions and develop targeted therapies.