C3 (inflammatory) and C4 (lymphocyte depleted) were the predominant immune subtypes in PPGLs, but interestingly they were represented differently according to tumor type; C3 was more abundant in non-metastatic tumors (52.3%), whereas C4 showed more prevalence among primary metastatic tumors and metastases (50.9 and 71.4%, respectively) (Fig. 6a). Here, C4A is linked to metastatic neoplasm.