To analyze the expression patterns of immunohistochemical markers CK20, CD10, PHLDA1, CD34, AR, Ber-EP4, and Ki-67 in cutaneous trichoblastoma (TB) and basal cell carcinoma (BCC), and validate their diagnostic value in differentiating TB from BCC.

Pathological specimens were harvested from 35 TB patients and 35 BCC patients diagnosed with histopathological biopsy in our department between January 2013 and December 2023. Their clinical data were collected, and the expression levels of CK20, CD10, PHLDA1, CD34, AR, Ber-EP4, and Ki-67 in TB and BCC tissues were detected with immunohistochemical staining. The staining patterns and proportions of positive cells in basaloid tumor nests and peritumoral stroma were analyzed. χ² test was used to screen statistically significant variables, and then multivariate logistic regression analysis was utilized to evaluate the diagnostic efficacy of each marker. Based on the significance of the markers, stepwise combinations of immunohistochemical markers were analyzed to determine their collective diagnostic performance.

Peripheral CD10 positivity in basaloid cell nests (P<0.001) and diffuse CD10 positivity in basaloid cells (P<0.001) strongly supported BCC diagnosis. In contrast, CK20 positivity in basaloid cells (P=0.028), CD10 positivity in stromal cells (P<0.001), and PHLDA1 positivity in basaloid cells (P<0.001) favored TB. Stromal CD34 positivity (P=0.247), AR positivity in basaloid cells (P=0.794), Ber-EP4 positivity in basaloid cells (P=0.156), Ki-67 proliferation index (P=0.280), and Ki-67 staining patterns (P=0.897) showed no significant differences between TB and BCC. Multivariate logistic regression analysis identified stromal CD10 positivity (P<0.001) and PHLDA1 positivity (P=0.042) as independent predictors of TB, showing negative correlations with BCC. CK20 positivity in basaloid cells (P=0.340) showed no statistically significant difference in expression between TB and BCC. The combination of stromal CD10, PHLDA1, and CK20 demonstrated the highest diagnostic performance (Youden index=0.74).

Stromal CD10 and basaloid PHLDA1 positivity serve as reliable markers for distinguishing TB from BCC.