Dermatofibroma vs dermatofibrosarcoma protuberans
- Lesion
Dermatofibroma is a common harmless firm bump. Dermatofibrosarcoma protuberans looks similar early on but keeps growing and comes back if not fully removed.
What it is
Dermatofibroma is a benign, often reactive, fibrohistiocytic nodule, typically on the legs of young and middle-aged adults, sometimes after minor trauma such as an insect bite. Dermatofibrosarcoma protuberans is a low-grade sarcoma of the dermis and subcutis driven by a COL1A1-PDGFB fusion; it infiltrates widely, recurs locally and rarely metastasises.
Dermatofibroma vs DFSP
| Feature | Dermatofibroma | Dermatofibrosarcoma protuberans |
|---|---|---|
| Behaviour | Benign | Low-grade sarcoma, local recurrence |
| Site | Legs | Trunk, proximal limbs |
| Depth | Dermis, limited | Dermis into fat (honeycomb) |
| Pattern | Haphazard fascicles, collagen trapping | Uniform storiform |
| Epidermis | Hyperplasia, basal pigment | Thinned, uninvolved |
| Markers | Factor XIIIa positive, CD34 negative | CD34 positive, factor XIIIa negative |
| Genetics | Clonal in some, usually none specific | COL1A1-PDGFB fusion |
Clinical notes
- DFSP needs wide or Mohs excision with clear margins.
- Dermatofibroma needs no treatment unless the diagnosis is uncertain.
Test yourself
Think of the answer, then tap the question to see it.
Which fusion drives dermatofibrosarcoma protuberans?
COL1A1-PDGFB, from t(17;22), often in a ring chromosome.
Which immunostain separates DFSP from dermatofibroma?
CD34 is positive in DFSP and negative in dermatofibroma (which is factor XIIIa positive).
Why does imatinib work in DFSP?
The fusion produces excess PDGF-B, and imatinib blocks the PDGF receptor tyrosine kinase.
Elsewhere in DurgiPedia
- Translocations, amplifications and epigenetic changes in cancer
- Immunohistochemistry: the principle and the markers to know
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Dermatofibrosarcoma protuberans (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.