Histiocytomas

What are histiocytomas?

Histiocytomas - also known as benign fibrous histiocytomas or dermatofibromas - are caused by an abnormal immune reaction to skin damage. They're harmless and can't turn into skin cancer.

Histiocytomas are common and usually develop as a reaction to something that disrupts the skin: a very tiny localised trauma such as a scratch or pin prick, for example, or an insect bite. Following the initial trauma, the immune system reacts with localised inflammation and a red itchy spot. Instead of settling and disappearing in a day or two, this spot then fills with fibrous cells and immune cells called histiocytes, forming a firm nodule.

This nodule is usually flesh-coloured, dark pink or brown. It may dimple in the centre if you squash it.

Histiocytomas usually develop in adults (rarely in children) and are most common on the arms and legs, although they can develop anywhere on the body.

Symptoms

Histiocytomas rarely get any bigger once they've formed. Neither do they often cause any symptoms or problems, although occasionally they can be a little uncomfortable, causing a sensation of pulling on the skin or as though a nerve is being caught.

Treatment and recovery

In most cases histiocytomas cause no symptoms, never get bigger and need no treatment. But in a few cases the nodule may be painful, unsightly or catch on clothing. In such cases it can usually be removed easily by a surgeon, using local anaesthetic. Go back to your GP if a histiocytoma causes you problems; otherwise, try to accept and live with them.