- A benign cutaneous neoplasm of the hair follicle
- Trichoepithelioma (TE) commonly presents as a solitary skin-colored papule or nodule on the face.
- Multiple lesions are seen in several autosomal dominant disorders including Brooke-Spiegler syndrome, Brooke disease, Rombo syndrome, and Bazex-Dupré-Christol syndrome.
- There are three variants of TE: (i) solitary, (ii) multiple familial TE (MFT), and (iii) desmoplastic TE (DTE).
- Can be mistaken for basal cell carcinoma (BCC) or Gorlin syndrome (multiple BCCs)
- Predominantly occurs in young adults
- Multiple lesions may occur in children and adolescents with associated autosomal dominant disorders.
- A distinct variation known as giant solitary TE may occur in the elderly.
- Rare (affects <1 person per 2,000)
- Female > male (2:1)
Etiology and Pathophysiology
- The short arm of chromosome 9 is known to encode proteins that can arrest the cell cycle by binding CDK4/6. Tumorigenesis is believed to occur when deletion or rearrangements near 9p21 inactivates these proteins, causing decreased CDK4 kinase binding and increased phosphorylation of the retinoblastoma tumor suppressor protein.
- Familial cases of TE are due a mutation of CYLD gene, a tumor suppressor gene that plays a role in deubiquitinating proteins. These proteins negatively regulate the nuclear factor-κB (NF-κB) signaling pathway. Loss of CYLD heterozygosity promotes tumor growth through continuous NF-κB activation, unregulated cell division, and resistance to apoptosis.
Commonly Associated Conditions
- Brooke-Spiegler syndrome
- Familial cylindromatosis (FC)
- Gorlin syndrome
- Rombo syndrome (atrophoderma, milia, hypotrichosis, TE, BCC, peripheral vasodilatation)
TE displays genetic heterogeneity; the two most prevalent mutations have been mapped to the following:
- 9p21 → Autosomal dominant mutation in a tumor suppressor gene gives rise to the familial form of TE (MFT).
- 16q12 to 16q13 (CYLD gene) → results in a spectrum of disease phenotypes including the following:
- Brooke-Spiegler syndrome, which demonstrates features of MFT and FC
- Female gender (due to increased disease penetrance)
- Family history
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