Dermatofibromas or Histiocytomas

What is a dermatofibroma?

A dermatofibroma, also known as a histiocytoma, is a common, harmless growth of fibrous tissue in the deeper layer of the skin (the dermis). Dermatofibromas are benign, which means they are not cancerous, and they do not become cancerous.

Who gets it?

Dermatofibromas are common. They are more common in women than men and usually appear in young to middle-aged adults.

What causes it?

The exact cause is not known. Many appear after a small skin injury, for instance a bite, a thorn or a nick while shaving, and may represent the skin's response to that injury. Some people, including those with a weakened immune system, develop several.

Is it hereditary or contagious?

There is no evidence that dermatofibromas are inherited. They are not contagious.

What does it look and feel like?

A dermatofibroma is a firm, slightly raised bump that feels like a small button under the skin. It is usually less than 1 cm across. The colour varies and can be pink, purple, brown or grey, often darker at the centre with a paler ring around it. On brown and black skin, dermatofibromas are often dark brown.

A characteristic feature is the dimple sign: when the skin on either side is gently pinched together, the dermatofibroma dimples inwards.

Dermatofibromas can appear anywhere, but they are most common on the legs, particularly the lower legs in women, and the upper arms. They are usually painless, but they can be itchy or tender and can be nicked when shaving.

How is it diagnosed?

A dermatofibroma is usually diagnosed from its appearance and feel, often with the help of a dermatoscope. If there is any doubt, for example if the lump is growing, changing or unusual, it may be removed and examined under the microscope to rule out other conditions, including rare skin cancers that can look similar.

What are the treatment options?

Dr Mounsey will confirm the diagnosis using a dermatoscope. As dermatofibromas are harmless, treatment is not needed. If one is troublesome or the diagnosis is uncertain, it can be removed by excision, which he carries out himself, but this leaves a scar that may be more noticeable than the original lump. Cryotherapy can flatten some dermatofibromas but may leave a pale mark. He will discuss whether removal is worthwhile.

What is the outlook?

Dermatofibromas are harmless. Most people have only one. Some fade or disappear on their own over time, while others stay the same for many years without causing any problems.

More information

British Association of Dermatologists patient leaflet: https://www.bad.org.uk/pils/dermatofibroma-also-known-as-histiocytoma

This page gives general information only and is not a substitute for a consultation. Everyone's skin is different, and what is right for you will depend on your own circumstances. If you are worried about a skin problem, please book an appointment with Dr Mounsey or speak to your GP. If you have a mole or skin lesion that is changing, bleeding or growing quickly, please seek medical advice promptly.