Furthermore, K15 is reported to be expressed suprabasally in differentiating keratinocytes of normal human esophagus [32,38] and in oral lichen planus [39], and in freshly-cut skin sections exposed to thyroid hormone or IFNγ [66], findings inconsistent with an undifferentiated keratinocyte phenotype, a distinctive feature of stem cells. This evidence concerns the gene KRT15 and oral lichen planus.