The Rate and Pattern of Bcl-2 and Cytokeratin 15 Expression in Trichoepithelioma and Nodular Basal Cell Carcinoma: A Comparative Study

CONTEXT: Histopathological evaluations can differentiate between clinically resembling trichoepithelioma (TE) and basal cell carcinoma (BCC) unless the biopsy specimens are small or superficial. Previous studies used immunohistochemical evaluation for Bcl-2 and cytokeratin 15 (CK15), in attempts to differentiate between these two entities, with heterogeneous findings. AIMS: This study intended to compare the rate and patterns of Bcl-2 and CK15 expressions between specimens of TE and nodular BCC. SETTINGS AND DESIGN: Case-series including formalin-fixed, paraffin-embedded cutaneous biopsies. SUBJECTS AND METHODS: Twenty-two BCC and 12 TE specimens were stained for Bcl-2 and CK15 and examined microscopically. The rate and patterns of expressions were compared between the two groups. STATISTICAL ANALYSIS USED: Statistical analysis was performed using the statistical software (SPSS version 16.0; SPSS Inc., Chicago, IL, USA), Pearson Chi-square, or Fisher's exact tests, wherever appropriate. RESULTS: The two groups were comparable for the expression rate and patterns of Bcl-2 (86.4%: 5 central, 14 diffuse in BCC vs. 83.3%: 2 central, 8 diffuse in TE; P = 0.59 and 0.54 for rate and pattern, respectively). The rate of CK15 expression was significantly higher in TE specimens (66.7%: 4 central, 3 diffuse, 1 peripheral vs. 4.5%: 1 central; P < 0.001). The positive likelihood ratio in distinguishing the two neoplasms was 14.7 (95% confidence interval: 2.1-103.7). CONCLUSIONS: CK15 but not Bcl-2 staining may help in differentiating between BCC and TE even in BCCs with follicular differentiation.