The human type II Cytokeratin 6 (CK6; 56 kDa) is well known for its strong induction in stratified epithelia that feature an enhanced cell proliferation rate or abnormal differentiation during wound healing, in several diseases (e.g. psoriasis, actinic keratosis) and in cancer. CK6 is expressed on stratified epithelia including oral mucosa, esophagus, basal layer of epidermis, the outer root sheath of hair follicles, and in glandular epithelia. CK6 is a marker of hyperproliferative and activated keratinocytes found in psoriasis. CK6 paired with CK5 is useful to differentiate mesothelioma (positive) from lung carcinoma (negative) or metastatic carcinoma (negative) in the pleura. CK5/6 has also been used to distinguish usual ductal hyperplasia of the breast (strong staining) from solid papillary DCIS (negative).