SLC40A1 and renal cell carcinoma: The results of bioinformatics analysis show that M2 macrophages may play a significant part in promoting the development of renal cell carcinoma by regulating the expression of M2 macrophage related genes such as SLC40A1, VSIG4, FUCA1, LIPA, BCAT1, CRYBB1, F13A, TMEM144 and COLEC12 in RCC.