This 79 year old man developed a single warty papule on his upper cutaneous lip. This is a typical clinical and histologic appearance of a trichilemmoma. One can see how it can be mistaken for a verruca, but to date, no virus has definitively been associated with a trichilemmoma. This is thought to be derived from the outer root sheath of the follicle, highlighted by the clear cell morphology of the lesion. Multiple trichilemmomas have an association with Cowden disease.
The epidermis is acanthotic and papillomatous. There is coarsening of the granular layer, accentuated in the divots of the papillations. There is an epithelial lesion with a smooth base and clear cell morphology.