Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1997. Updated January 2016.
A dermatofibroma is a common benign fibrous nodule that most often arises on the skin of the lower legs.
A dermatofibroma is also called a cutaneous fibrous histiocytoma.
It is not clear if dermatofibroma is a reactive process or if it is a neoplasm. The lesions are made up of a proliferation of fibroblasts. Histiocytes may also be involved.
They are sometimes attributed to an insect bite or rose thorn injury, but not consistently. They may be more numerous in patients with altered immunity.
Dermatofibromas most often occur on the legs and arms, but may also arise on trunk or any site of the body
Because they are often raised lesions, they may be traumatised, for example by a razor.
Occasionally dozens may erupt within a few months, usually in the setting of immunosuppression (for example autoimmune disease, cancer or certain medications).
Dermatofibroma does not give rise to cancer. However, occasionally, it may be mistaken for dermatofibrosarcoma or desmoplastic melanoma.
Dermatofibroma is usually easy to diagnose clinically, supported by dermatoscopy. The most common dermatoscopic pattern is a central white area surrounded by faint pigment network.
The histology shows whirling fascicles of spindle cell proliferation with excessive collage deposition in the dermis. There are several pathological variants of dermatofibroma.
In case of doubt, immunohistochemical staining is used to confirm the diagnosis.
A dermatofibroma is harmless and seldom causes any symptoms. Usually only reassurance is needed. If it is nuisance or causing concern, the lesion can be removed surgically.
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