FAP and neoplasm: Attention has been peculiarly focused on dipeptidyl peptidase 4 (DPP4, CD26), fibroblast activation protein alpha (FAP, Seprase), aminopeptidase N (APN, CD13), and ADAM17 (also known as tumour necrosis factor-α-converting enzyme/TACE), whose deregulated expression in the tumour microenvironment (TME) is correlated with a malignant cancer phenotype (tumour cell growth, survival, metastasis, and tumour-associated angiogenesis) [2,3,4,5,6,7,8,9,10,11,12,13,14] (Figure 1).