ACTA1 and cancer: Although fibroblasts within cancers comprise a phenotypically heterogeneous population, and the terminology is confusing [peritumour fibroblasts, cancer-associated fibroblasts (CAFs), ‘activated’ fibroblasts], ‘activated’ CAFs are commonly described as having a myofibroblastic phenotype; ie a secretory and contractile cell which expresses α-smooth muscle actin (α-SMA) [14,15].