This review discusses novel tumor-associated macrophage (TAM) subpopulations identified through single-cell RNA sequencing (scRNA-seq) in solid tumors. Four TAM subpopulations—FCN1+, SPP1+, C1Q+, and CCL18+—were identified based on core gene signatures. These subpopulations exhibit distinct functional roles in tumor progression, including inflammation, metastasis, angiogenesis, and immunosuppression. FCN1+ TAMs are inflammatory macrophages, while SPP1+ TAMs are involved in metastasis, angiogenesis, and cancer stem cell activation. C1Q+ TAMs play a key role in immunosuppression, and CCL18+ TAMs have stronger immunosuppressive functions and enhance tumor metastasis. These subpopulations can be further divided into distinct functional groups. The study highlights the importance of these TAM subpopulations in tumor biology and their potential as therapeutic targets. However, there is a potential disconnect between the cell types identified by scRNA-seq and their actual functions. The review also discusses the origin of TAMs, including their embryonic and monocyte origins, and their differentiation into distinct subpopulations. The study emphasizes the need for further research to clarify the exact functions of these TAM subpopulations to develop targeted therapies. The review concludes that scRNA-seq is a powerful tool for identifying TAM subpopulations and understanding their roles in tumor biology.This review discusses novel tumor-associated macrophage (TAM) subpopulations identified through single-cell RNA sequencing (scRNA-seq) in solid tumors. Four TAM subpopulations—FCN1+, SPP1+, C1Q+, and CCL18+—were identified based on core gene signatures. These subpopulations exhibit distinct functional roles in tumor progression, including inflammation, metastasis, angiogenesis, and immunosuppression. FCN1+ TAMs are inflammatory macrophages, while SPP1+ TAMs are involved in metastasis, angiogenesis, and cancer stem cell activation. C1Q+ TAMs play a key role in immunosuppression, and CCL18+ TAMs have stronger immunosuppressive functions and enhance tumor metastasis. These subpopulations can be further divided into distinct functional groups. The study highlights the importance of these TAM subpopulations in tumor biology and their potential as therapeutic targets. However, there is a potential disconnect between the cell types identified by scRNA-seq and their actual functions. The review also discusses the origin of TAMs, including their embryonic and monocyte origins, and their differentiation into distinct subpopulations. The study emphasizes the need for further research to clarify the exact functions of these TAM subpopulations to develop targeted therapies. The review concludes that scRNA-seq is a powerful tool for identifying TAM subpopulations and understanding their roles in tumor biology.