FAP and neoplasm: This cell-type is mostly defined based on morphological characteristics, biological behavior (including promotion of tumor cell growth) [13] or the expression of markers such as a-smooth-muscle actin (a-SMA), fibroblast-activated protein (FAP), fibroblast-specific protein-1 (FSP1), neuron-glial antigen-2 (NG2) and PDGF β-receptor [10].