The field of tumor immunology has evolved into a pivotal discipline bridging cancer biology and immunology, focusing on deciphering the dynamic interplay between tumors and host immune defenses. Current research highlights the dual role of immune cells in both suppressing and promoting tumor progression, with emerging insights into mechanisms of immune evasion—such as regulatory T-cell infiltration, myeloid-derived suppressor cell (MDSC) activity, and metabolic reprogramming of tumor-associated macrophages (TAMs). Advances in multi-omics, spatial transcriptomics, and AI-driven analytics are revolutionizing our understanding of tumor antigens, immune checkpoints, and microenvironmental crosstalk.