TREM2 and melanoma: Moreover, a recent study examined brain metastases from different cancer types (melanoma, breast, lung, ovarian, colorectal, and renal cancer) and revealed a cluster of TREM2+ macrophages (APOE, SPP1, C1QA-C, APOC1, FCGR3A) [75], supporting a possible impact of TREM2 in the metastatic process.