Sean Klepper M.D.
Artur Zembowicz M.D....
- Benign tumor occurring on the head and neck of adults
- Presents as a small skin-colored nodule with a central keratin plug and multiple vellus hairs
- Dilated primary hair follicle lined by infundibular or isthmic-type epithelium with an opening onto the epidermal surface
- Multiple smaller secondary hair follicles bud off the primary follicle, with the formation of germinative epithelium or mature hairs.
- The dermal collagen in and around the lesion is densely collagenized in parallel layers, with a sharp demarcation with the surrounding dermis.
- A variety of cell types are present within the hair follicle structures: isthmic, clear cells with nuclear palisading, basaloid matrical cells.
- Foci of sebaceous differentiation are sometimes seen. When large sebaceous follicles connect to the central cavity of the primary follicle, the term sebaceous trichofolliculoma may be used.