Myofibroblasts, in general, express α-smooth muscle actin (αSMA), as well as vimentin, desmin, cadherin11 and collagen type 1; however, due to their diverse origins, including trans-differentiation from adipocytes, epithelial and endothelial cells, or differentiation from mesenchymal stem cells (MSCs) [9,10] that account for approximately 20% of myofibroblasts in the tumour microenvironment [9,11,12], it has proven difficult to define a set of markers that can be used to robustly define them [10,13]. The gene discussed is ACTA1; the disease is neoplasm.