The Importance of Cytokeratin 19 Expression in the Differentiation of Basal Cell Carcinoma and Trichoepithelioma

Introduction: Basal cell carcinoma (BCC) is the most common skin neoplasm reported in human. On the other hand, trichoepithelioma (TE) is a rare, benign tumour of skin adnexa. The differentiation of BCC and TE may be difficult since their morphological findings are similar. In a few studies, it has been determined that undifferentiated basaloid cells are highly positively stained with cytokeratin 19. Aim: The aim of this study was the comparison of cytokeratin 19 expression in cases of BCC and TE. Materials and Methods: Sections of skin tissues of 17 TE, 25 BCC and 12 non-neoplastic cases were used for cytokeratin 19 (CK19) immunohistochemical staining. Results: Staining with CK19 of the BCC cases gave 15(60%) diffuse, 7 (28%) focal and 3 (12%) negative staining. On the other hand, among TE cases, 2 (12%) gave diffuse, 5 (29%) focal and 10 (59%) negative staining with CK19. In the nonneoplastic skin tissue samples, while positive staining with cytokeratin 19 in the outer root sheath of hair follicles and sweat glands were observed, there was no staining in basal layers. Conclusion: CK19 expression may be helpful in the differential diagnosis of BCC and TE especially in small skin biopsy samples in which morphologic differentiation is difficult.