TREM2 and cancer: Characteristics of TREM2(+) TAMs:1. Functionally, they are more similar to M2-type TAMs;2. They are involved in the activation of the complement system, leading to the disruption of the cancer immunity cycle;3. They upregulate PD-L1 on the surface of TAMs, thereby reducing the anti-tumor effects of T cells;4. They highly express soluble factors, making them an ideal target for liquid biopsy.