Fibrous Histiocytoma (Dermatofibroma)
(DF)
Epidemiology:
Common sites:
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
- Grenz zone between epidermis and lesion
- rare mitoses
- histiocytic variant:
- giant cells and xanthomatous histiocytes
in a fibrous background
- abundant hemosiderin
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Factor XIIIa
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CD34 (neg)
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Molecular features:
Other features: