Practice Essentials
Trichofolliculoma represents an uncommon hamartoma of hair follicle tissue, typically occurring on the face of adults.[1] Notably, trichofolliculomas have been reported on the eyelids, auricle, and external auditory canal.[2, 3, 4]
View Image | Clinical appearance of trichofolliculoma. |
The prognosis is excellent, and therapy is usually directed toward cosmetic improvement.
Pathophysiology
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.
Prognosis
The prognosis is excellent. Although reports exist of recurrence at the primary site, these events are rare. Trichofolliculomas are associated with minimal clinical morbidity; no confirmed cases of malignant transformation or clinical mortality are reported in the literature.
History and physical examination
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).
Classic trichofolliculomas have a central pore or black dot, possibly draining a sebaceouslike material. A tuft of white hair may be present emerging from the central pore.
Causes
Usually, these tumors develop spontaneously. Rarely, a prior history of trauma at the tumor site is obtained.
Diagnostics
See Workup.
Treatment
Simple surgical excision is typically curative.
Epidemiology
Trichofolliculoma represents an uncommon clinical entity. 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.[5]
From published reports, trichofolliculoma appears to primarily be a tumor of adults; however, at least 2 cases of congenital trichofolliculoma have been reported.[6, 7]
Histologic Findings
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.[12]
View Image | 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.
View Image | Edge of the primary follicle with associated secondary and tertiary budding follicular structures. |
View Image | 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.
View Image | Low-power view of a section of trichofolliculoma demonstrating budding follicular structures and associated stroma. |
View Image | 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.[13]
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.[14, 15] 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.[16]
View Image | Higher magnification of central primary follicle and associated sebaceous lobules. |
Other Tests
In a single trichofolliculoma case, Karaarslan et al reported reflectance confocal microscopy (RCM) findings. A honeycomb pattern with some disarray was noted at the epidermal level. Although there were no atypical cells, some bright inflammatory cells were present. The epidermal thickness was lessened. Rings were scarce at the dermoepidermal junction. Additionally, squamous hyperplasia was present, comprising irregular finger-like protrusions circumscribing the hair follicle. Papillomatous hyperplasia in the hair follicle epithelium was also noted. Coarse collagen fibers beneath the follicles were present at the dermal level.[17]
Author
Michael S Howard, MD, Dermatopathologist and Laboratory Director, Georgia Dermatopathology Associates
Disclosure: Nothing to disclose.
Specialty Editors
Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Disclosure: Nothing to disclose.
Rosalie Elenitsas, MD, Herman Beerman Professor of Dermatology, University of Pennsylvania School of Medicine; Director, Penn Cutaneous Pathology Services, Department of Dermatology, University of Pennsylvania Health System
Disclosure: Received royalty from Lippincott Williams Wilkins for textbook editor.
Chief Editor
Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
Bruce R Smoller, MD, Executive Vice President, United States and Canadian Academy of Pathology
Disclosure: Nothing to disclose.
James W Patterson, MD, Professor of Pathology and Dermatology, Director of Dermatopathology, University of Virginia Medical Center
Disclosure: Nothing to disclose.
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