Desmoplastic trichoepithelioma: the association with compound nevus and ossification.

We report two cases of desmoplastic trichoepithelioma. One case was associated with compound nevus and the other case with ossification. Desmoplastic trichoepithelioma and nevus cell nevus are assumed to be a combined malformation. In our case 1, clinical and histological findings indicate that nevus cell nevus preceded desmoplastic trichoepithelioma and the latter developed in the lesion of the former. Ossification was reported to be associated with desmoplastic trichoepithelioma in 6% of cases. However, case reports of this combination with a detailed description are extremely rare. We speculate that the mechanism of ossification in this tumor must be related to foreign-body reactions caused by ruptured horn cysts.