Cytokeratin 15 (KRT15, CK15) is an Type I cytokeratin that is found in the basal cells of the squamous epithelium of the cervix, the conjunctiva and corneal limbus, esophagus, oral mucosa, developing ureters, fetal hair follicles and nails, breast, prostate, and deep rete ridges of adult skin. It is also a marker of stem cells of the hair-follicle bulge. It is downregulated in psoriasis and wound injury and positive in benign or low-grade sebaceous neoplasms and trichoepitheliomas. References: Smedts Am J Pathol 1993 142(2):403; Tai 2013 PLos One 8(11):e81167; Webb Differentiation 2004 72(8):387; Exp Cell Res 2000 254:80; J Cut Pathol 2006 33(9):634