Study of immunohistochemical expression of cytokeratin 17 in basal cell carcinoma

Background Basal cell carcinoma (BCC) is the most common malignant neoplasm in humans. However, it has not been distinctly clarified as to which primary cell gives rise to BCCs. Cytokeratin 17 (CK 17) is normally expressed in human epithelial appendages, including hair follicles, and is considered a marker of follicular differentiation. O¨ bjective To investigate the expression of CK 17 in BCC by means of immunohistochemical studies. Materials and methods This study included 20 paraffin blocks of BCC and 20 paraffin blocks of normal skin as control. All were subjected to hematoxylin and eosin staining and immunohistochemical staining for CK 17. Results CK 17 showed a diffuse positive expression in all studied BCCs, without significant differences between the different subtypes neither in intensity nor in extent. In addition, in morpheaform BCC, CK 17 immunostaining clearly detected individual tumor cells away from the dermal tumor strands. Conclusion The pattern of CK 17 expression provided an additional evidence to the suggestion that the tumorous differentiation in BCC is toward follicular outer root sheath cells and glandular components of the pilosebaceous-apocrine unit. Moreover, the intensity of CK 17 expression may not necessarily correlate with the more aggressive behavior generally associated with the morpheaform BCC variant. CK 17 is a useful marker in the identification and outlining of BCC.