Trichofolliculoma represents an uncommon hamartoma of hair follicle tissue, typically occurring on the face of adults.
Clinical appearance of trichofolliculoma.
The prognosis is excellent, and therapy is usually directed toward cosmetic improvement.
Although the precise etiology of trichofolliculoma is uncertain, these tumors are not associated with systemic disease or other skin disorders. Trichofolliculomas are believed to represent abortive differentiation of pluripotent skin cells toward hair follicles.
Trichofolliculoma represents an uncommon clinical entity.
Trichofolliculomas are associated with minimal clinical morbidity; no confirmed cases of malignant transformation or clinical mortality are reported in the literature.
In reported cases, trichofolliculomas demonstrate no definitive racial predilection.
No definitive sexual predilection is observed in reported cases, although sporadic reports indicate a probable male preponderance.
From published reports, trichofolliculoma appears to primarily be a tumor of adults; however, at least 1 case of congenital trichofolliculoma has been reported.
Patients typically present with a single, flesh-colored or whitish nodule or papule of varying duration, typically on the face (most frequently around the nose).
Following surgical excision, these tumors are found to consist of a dilated primary follicle lined by infundibular, stratified squamous epithelium and opening to the skin surface.
Low-power view of trichofolliculoma with a primary follicle opening onto the skin surface.
From the central follicle outward, numerous secondary and tertiary follicles can be observed, presenting at various levels of hair-follicle differentiation. Hair structures may be observed within the hair follicle lumen; small sebaceous elements may be found within the follicular units.
Edge of the primary follicle with associated secondary and tertiary budding follicular structures.
Higher magnification of budding follicular structures.
Minimal lymphocytic or granulomatous inflammation may be present. An abundant connective tissue stroma is also present surrounding the follicular structures.
Low-power view of a section of trichofolliculoma demonstrating budding follicular structures and associated stroma.
Higher magnification of budding follicular structures and associated stroma.
Abundant Merkel cells have been demonstrated within the follicular epithelium, supporting the concept that trichofolliculomas are hamartomas.
A variant of the trichofolliculoma is the sebaceous trichofolliculoma, featuring similar histologic features, except for the presence of numerous well-differentiated sebaceous lobules emptying into the central, dilated primary follicle. Sebaceous trichofolliculoma demonstrates histologic overlap with folliculosebaceous cystic hamartoma.[6, 7] Some consider the latter tumor to be a sebaceous trichofolliculoma in telogen phase. A single case of trichofolliculoma with perineural invasion has been reported in the literature.
Higher magnification of central primary follicle and associated sebaceous lobules.
Simple surgical excision is typically curative.
The prognosis is excellent. Although reports exist of recurrence at the primary site, these events are rare.