Fibrous Histiocytoma (Dermatofibroma) (DF)

 

Epidemiology:

    • Middle-aged women

 

Common sites:

    • Legs

 

Gross features:

    • Firm
    • Tan to brown
    • Papule
    • Majority < 1cm
    • Tender
    • Dimple inward on lateral compression

 

Histologic features:

    • ill-defined dermal nodule
      • not invading fat or minimal involvement of fat
    • spindle cells haphazardly arranged in short bundles
    • trapping of hyalinized collagen bundles at the periphery
      • spindle cells wrapped around collagen bundles
    • irregular acanthosis of overlying epidermis
      • basal hyperpigmentation
    • Grenz zone between epidermis and lesion
    • rare mitoses
    • histiocytic variant:
      • giant cells and xanthomatous histiocytes in a fibrous background
      • abundant hemosiderin

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Factor XIIIa

 

 

CD34 (neg)

 

 

 

Molecular features:

    •  

 

Other features:

    •