As CK14 is a marker of the basal epidermal layer which comprises the epidermal stem cells [60], and as MCs in mice have CK14-positive progenitors [22–24], the authors argued that a malignant transformation of epidermal stem cells could underlie MCC, and that the transformed cells could then serve as cancer stem cells for MCC [59]. The gene discussed is KRT14; the disease is cancer.