Trichofolliculoma ( Hair Follicle Tumors)
The trichofolliculoma is a hamartomatous process representing an aborted and disrupted attempt at hair follicle formation. This tumor is analogous to the odontoma or ameloblastic fibro-odontoma of the jaws, which represents an aborted and disrupted attempt at tooth formation. The trichofolliculoma arises from the midshaft area of the hair follicle and seems to mark a disturbance between the normal epidermal and the dermal cell components of the hair follicle cycle.
- Clinically, trichofolliculomas are usually irregular papules ranging from 1 to 4 cm that may have tufts of white hair emerging from their surface.
- Larger ones have a surface that is dome shaped with a reddened base and yellow surface crusting.
- Smaller ones have a normal surface color, a regular shape, and a central pore with a white or gray hair emerging from it.
Depending on their size and shape, trichofolliculomas may resemble most of the common sun damage-related tumors:
- basal cell carcinoma, and
- skin squamous cell carcinoma.
Those with a reddened base and yellow crusting may mimic skin infections, particularly
- folliculitis and
- infected epidermoid cysts.
The architecture is of major significance and shows a dilated follicular structure with secondary follicles developing from it. The degree of differentiation of the secondary follicles is variable. There is a well-organized fibrous stroma.
Trichofolliculomas are treated with a local excision with 2-mm margins and should include the subcutaneous layer deep to the tumor. Such an excision should be curative without recurrence. Recurrences should raise suspicion of an unrecognized malignancy.