Desmoplastic trichoepitheliomas commonly occur on the face of young women, as was seen in this case. The differential diagnosis includes other sclerosing tumors such as morpheaform basal cell carcinoma and microcystic adnexal carcinoma. Helpful clues include the clinical presentation, the presence of keratin cysts and calcification, lack of more typical nodular basal cell carcinoma or peritumoral clefting, and the overall circumscription of the lesion (not appreciated in this particular case). This is an important differential because trichoepitheliomas are thought to be benign hamartomatous lesions while the others are malignant. We would recommend complete excision in either case.
At higher power of the same lesion, the bland nature of the cysts and cords is appreciated. Focal sebaceous differentiation is noted.