Distinguishing Trichoepitheliomas from Basal-Cell Carcinomas

Trichoepitheliomas, benign follicular neoplasms, are often difficult to distinguish, both clinically and histologically, from basal-cell carcinomas. Both tumors frequently occur on the face in adults and have a similar appearance. Histologically, both tumors are formed of collections of basaloid cells demonstrating follicular differentiation, set in a stroma in the upper dermis. Features that can help distinguish basal-cell carcinomas from trichoepitheliomas are the presence of peripheral palisading of keratinocytes, clefting between the epithelial and stromal components of the tumor, single-cell necrosis, and a brisk mitotic rate, but in many cases these features are not evident. Because the two tumor types have a different prognosis and a…