Skin nonmelanocytic tumor

Adnexal tumors

Hair follicles

Trichofolliculoma



Minor changes: 9 December 2021

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PubMed Search: Trichofolliculoma [title]

Sepideh Nikki Asadbeigi, M.D.
Cuong Nguyen, M.D.
Page views in 2021: 13,419
Page views in 2022 to date: 849
Cite this page: Asadbeigi SN, Nguyen C. Trichofolliculoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocytictrichofolliculoma.html. Accessed January 23rd, 2022.
Definition / general
  • Benign adnexal hamartomatous follicular tumor
  • Histologically shows multiple follicles in various stages spreading from a central cystic follicle
Essential features
  • Solitary papule in adults in the head and neck region
  • Central dilated primary follicle with secondary follicles budding from the primary follicle
  • Can show a spectrum of morphology depending on the hair follicle cycle
ICD coding
  • ICD-O: 839 - 842 - adnexal and skin appendage neoplasms
  • ICD-10: D23.9 - other benign neoplasm of skin, unspecified
Epidemiology
Sites
Pathophysiology
  • Mesenchymal follicular differentiation (J Dermatol 2017;44:1050)
  • Repeated development of hair follicles with disordered hair cycle; defective sonic hedgehog polarization (J Dermatol 2017;44:1050, Am J Dermatopathol 2009;31:248)
  • Distorted ability to control the size of hair follicles
  • Trichofolliculoma with sebaceous differentiation: follicular and sebaceous components have independent cycles
  • Primary follicle:
    • Primary infundibular cystic structures show thickening of the epithelium and outer root sheath differentiation
    • Decrease in the number of secondary vellus follicles and shift from anagen to catagen phase
  • Secondary follicles:
    • Out of control hair cycle
  • Tertiary hair follicles:
    • Anagen hair randomly develops from the involuting secondary follicles in association with a reduction in the number of secondary follicles
    • Anagen tertiary or quaternary follicles without the replacement of regressing secondary follicles
Clinical features
Diagnosis
  • Clinical: central primary follicle with multiple tufts of vellus hair (Am J Pathol 1976;85:479)
  • If the hair is plucked, trichofolliculoma can be clinically misdiagnosed as basal cell carcinoma, molluscum contagiosum, keratoacanthoma, milium, trichoepithelioma, syringoma or sebaceous hyperplasia (J Eur Acad Dermatol Venereol 2017;31:e123)
  • Dermoscopy: shows troll hair sign - tight plumes of white and thin hairs, similar to children's troll dolls (Australas J Dermatol 2021;62:90)
  • Biopsy and histological examination
Prognostic factors
Case reports
Treatment
Clinical images

Contributed by Sepideh Nikki Asadbeigi, M.D.
Trichofolliculoma

Trichofolliculoma



Images hosted on other servers:

Papule with white vellus hair

Microscopic (histologic) description
  • Dilated central cystic follicle with surrounding multiple fully formed vellus follicles
  • Early lesion: a mildly dilated infundibulum and radiating secondary curved vellus follicles; cystic dilatation may be absent
  • Late lesion: thin walled primary infundibular cystic structure and radiating vellus or terminal follicles that are mostly in the anagen phase
  • Trichofolliculoma demonstrates outer root sheath differentiation
  • Central follicle shows stratified squamous cell epithelium with a granular layer with dilation or cystic changes and contains keratinous material and may have vellus hairs
  • Primary follicle has keratinized stratified epithelium with keratohyaline granules
  • Branched follicles may show varying degree of maturation, including rudimentary structures or epithelial cords and anagen, catagen or telogen hair in older lesions
  • Secondary follicles are small with many epithelial strands and abortive pilar formation
  • Sebaceous differentiation may be present
  • Trichofolliculoma is usually surrounded by well developed connective tissue, which is frequently cellular
  • Late stage can show a solid pattern as the regressing secondary follicles and developing tertiary follicles coalesce
  • Sebaceous trichofolliculoma variant: sebaceous gland attached to radiating follicles (J Cutan Pathol 1980;7:394)
Microscopic (histologic) images

Contributed by Sepideh Nikki Asadbeigi, M.D.
Primary and secondary follicles

Primary and secondary follicles

Secondary follicles

Secondary follicles

Primary cystic follicle

Primary cystic follicle

Dilated hair follicle

Dilated hair follicle

Secondary hair follicle

Secondary hair follicle

Virtual slides

Images hosted on other servers:
Trichofolliculoma with sebaceous differentiation

Trichofolliculoma with sebaceous differentiation

Positive stains
Molecular / cytogenetics description
Videos

Trichofolliculoma clinical and pathology by Dr. Michael Lee

Trichofolliculoma histopathology by Dr. Jerad Gardner

Sample pathology report
  • Forehead skin, shave biopsy:
    • Trichofolliculoma (see comment)
    • Comment: Atypia is not identified.
    • Microscopic description: Sections demonstrate a centrally dilated follicular unit with multiple radiating follicular units. At the center of the cystic structure there is keratotic debris and immature hair shafts (trichoids). Surrounding the structure is a mantle of well organized connective tissue. Atypical features were not noted.
Differential diagnosis
  • Trichoadenoma:
    • Multiple multilayered squamous epithelial islands with a central cystic cavity containing keratinous material
    • Does not contain hair shafts
  • Solitary trichoepithelioma:
    • Islands of basaloid cells are present, which is not a feature of trichofolliculoma
  • Fibrofolliculoma:
    • Both show a large central follicle with multiple arising epithelial attachments
    • Fibrofolliculoma only has strands of follicular epithelium and does not contain any hair shafts
  • Dilated pore of Winer:
    • Widened follicular infundibulum
    • Unlike trichofolliculoma, it does not show the radiating secondary follicles
  • Hair follicle nevus:
    • Both lesions show multiple hair follicles with vellus hairs but trichofolliculoma has a central cystic component
  • Follicular infundibulum cyst:
    • Does not contain the secondary or tertiary follicular structures
  • Pilar sheath acanthoma:
    • Less florid pattern than trichofolliculoma
    • Dilated central follicle with cystic features and radiating acanthotic epithelium
    • Unlike trichofolliculoma, pilar sheath acanthoma does not have hair shafts in the peripheral buds
  • Folliculosebaceous cystic hamartoma:
    • Folliculosebaceous structures with surrounding stroma with various mesenchymal elements
    • Sebaceous component is the more prominent component
    • Although it has been suggested that this is a late stage of sebaceous trichofolliculoma, reports of congenital folliculosebaceous cystic hamartoma suggest that this idea is incorrect (Am J Dermatopathol 2008;30:500, J Cutan Pathol 2008;35:843)
Additional references
Board review style question #1

A 50 year old Caucasian woman presents with a solitary flesh colored papule with a central depression. What is the diagnosis?

  1. Dilated pore of Winer
  2. Pilar sheath acanthoma
  3. Trichoepithelioma
  4. Trichofolliculoma
Board review style answer #1
D. Trichofolliculoma

Comment Here

Reference: Trichofolliculoma
Board review style question #2
The biopsy of a skin colored papule on the face of a 34 year old man shows a central dilated follicle with smaller radiating follicular units containing hair shafts. What is the most accurate diagnosis?

  1. Hair follicle nevus
  2. Pilar sheath acanthoma
  3. Trichoadenoma
  4. Trichofolliculoma
Board review style answer #2
D. Trichofolliculoma

Comment Here

Reference: Trichofolliculoma
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