Cytokeratin-19 (Keratin, type I cytoskeletal 19) is involved in the organization of myofibers. Cytokeratin-19 together with KRT8, helps link the contractile apparatus to dystrophin at the costameres of striated muscle. Cytokeratin-19 is expressed in a defined zone of basal keratinocytes in the deep outer root sheath of hair follicles. Cytokerating-19 is also observed in sweat gland and mammary gland ductal and secretory cells, bile ducts, gastrointestinal tract, bladder urothelium, oral epithelia, esophagus, ectocervical epithelium.