Trichoepithelioma

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Basics

Description

  • 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)

Epidemiology

  • 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.

Incidence
Incidence unknown

Prevalence

  • 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)
  • BCC
  • Gorlin syndrome
  • Rombo syndrome (atrophoderma, milia, hypotrichosis, TE, BCC, peripheral vasodilatation)

Genetics
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:
    • MFT
    • FC
    • Brooke-Spiegler syndrome, which demonstrates features of MFT and FC

Risk Factors

  • Female gender (due to increased disease penetrance)
  • Family history

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Basics

Description

  • 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)

Epidemiology

  • 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.

Incidence
Incidence unknown

Prevalence

  • 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)
  • BCC
  • Gorlin syndrome
  • Rombo syndrome (atrophoderma, milia, hypotrichosis, TE, BCC, peripheral vasodilatation)

Genetics
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:
    • MFT
    • FC
    • Brooke-Spiegler syndrome, which demonstrates features of MFT and FC

Risk Factors

  • Female gender (due to increased disease penetrance)
  • Family history

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