TREM2 and hepatocellular carcinoma: Upon the development of HCC, the hypoxic microenvironment triggers M2 polarization in macrophages, and tumour cells recruit TREM2+ macrophages with an M2 phenotype through the CCL15‐CCR1 axis, which promotes the formation of an immunosuppressive microenvironment and facilitates immune evasion by tumour cells.