Dermatofibroma

What is a dermatofibroma?

A dermatofibroma is a common benign fibrous skin lesion.

A dermatofibroma is also sometimes called a fibrous histiocytoma. It is due to a non-cancerous growth of dermal dendritic histiocyte cells. In some cases it arises at the site of a minor injury, especially an insect bite or thorn prick. The cause is unknown; wehether it is due to a neoplasm or reactive process is debated.

What does it look like?

Dermatofibromas most often occur on the legs and arms. Once developed, they usually persist for years. They appear as firm-feeling nodules, often yellow-brown in colour, sometimes pink and sometimes quite dark, especially in dark coloured skin. If the skin over a dermatofibroma is squeezed a dimple forms, indicating tethering of the skin to the underlying fibrous tissue.

Dermatofibroma

	Pinch sign	Dermoscopic view

More images of dermatofibroma ...

Multiple dermatofibromas

It is not uncommon for people to have several dermatofibromas. Occasionally dozens may erupt within a few months, in the setting of immunosuppression (for example autoimmune disease, cancer or certain medications).

Investigations

A skin biopsy may be recommended to confirm the nature of the skin lesion. The pathology report may describe one of several variants of dermatofibroma.

• cellular
• aneurismal
• epithelioid
• atypical
• lipidized ankle-type
• palisading
• cholesterotic

The pathologist will examine the tissue carefully and make sure there is no sign of skin cancer, particularly dermatofibrosarcoma or the desmoplastic form of melanoma.

Treatment

A dermatofibroma is of cosmetic significance only and although it tends to persist long term, it seldom causes any symptoms. Usually only reassurance is needed. Sometimes its dark colour can raise anxiety about melanoma; if there is any doubt about its nature, the lesion can be excised for histology.

Other techniques are freezing the lump with liquid nitrogen to flatten it out but this is rarely completely successful and may leave a white mark behind.