Table 3 Useful histological and immunohistochemical features for distinguishing between basal cell carcinoma and trichoepithelioma.

Feature	BCC	TE
Histology	Increased mitoses	Mitoses not increased
	Retraction spaces	Retraction spaces not present
	Usually no horn cysts	Horn cysts usually present
Stromelysin 3	Positive in stroma	Negative
CD10	Positive in basaloid cells	Positive in stroma
CD34	Negative	Positive in stroma
Bcl‐2	Diffusely positive in basaloid cells	Positive in peripheral cells only
Ki‐67	Increased (20–40%)	Normal (rare cells)
CK 15	Negative	Focally positive
CK 20	Negative	Focally positive

BCC, basal cell carcinoma; CK, cytokeratin; TE, trichoepithelioma.