Case Discussion
Trichilemmoma is a benign tumour of the hair follicle, arising in the outer root sheath. Sections show epidermal based proliferation (related to the follicular root sheath) of uniform small cells with peripheral palisading and adjacent hyalinized basement membrane. Clear cell change can be seen due to intracytoplasmic glycogen. Multiple lesions are associated with Cowden disease, with mutation in PTEN gene.
