Trichoepithelioma

 

Epidemiology and Etiology:

    • Young to middle aged adults
    • Multilpe lesions in autosomal dominant familial form

 

Common sites:

    • face

 

Gross features:

    • papule
      • flesh-coloured

 

Histologic features:

    • keratin-filled cysts
    • trabeculae of basaloid cells
    • mild to moderate fibrosis in surrounding dermis
      • well-demarcated from normal dermis
      • stromal-stromal separation present
    • papillary mesenchymal bodies
      • fibroblastic proliferations attempting to construct papillary mesenchyme
    • peripheral palisading present
    • No stromal retraction
    • no mucin production (except rarely)
    • no stromal reaction
    • low apoptotic rate
    • low mitotic rate

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

CK 15, 20 (focal)

(neg in BCC)

 

 

 CD34 (stroma)

(neg in BCC)

 

 

Bcl-2 (only outermost epithelial layer)

(diffuse in BCC)

 

 

Ki-67 (normal)

(increased in BCC)

 

 

 

Molecular features:

    •  

 

Other features:

    •  

 

References:

    • Barnhill 2004