Trichoblastic Fibroma

—Report of a Case and Differential Diagnosis from Keratotic Basal Cell Epithelioma and Solitary Trichoepithelioma—

Abstract

A 69-year-old man with trichoblastic fibroma on the posterior aspect of right thigh was treated. Histopathologically, the oval tumor contained epithelial and stromal components in the dermis. Basaloid cells, epithelial components, showed no continuity to the epidermis, and nests of basaloid cells were embedded in the fibrous stroma. Some of nests showed a protrusion-like primary epithelial germ. Cords of one or two rows of the basaloid cells were also observed. Differential diagnosis was made on both the keratotic basal cell epithelioma and solitary trichoepithelioma. The former grows rapidly and there is ulcer formation. Basaloid cells show continuity to the epidermis and cleft to stroma with inflammatory infiltration. The pattern of growth is destructive. The latter shows continuity to the epidermis with well developed, numerous horn cysts. Cords of the basaloid cells invaginate and have an immature follicular papillae. It was concluded that trichoblastic fibroma comes in the middle of these two tumors, from the grade of differantiation to the follicle.