The lesion projects upwards from the skin surface in the shape of a dome. The colours of dermatofibroma vary. The classical DF has a pink or flesh-coloured centre with a pale brown periphery. Other colours are orange, yellow, red, or sometimes even purple, blue, or black. The size ranges from 3 to 10mm.
When squeezed between the finger and thumb, the hard nodule sinks below the skin (the “dimple sign”). Don’t pinch too deep! Just pinch the surface of the skin to feel a very firm lesion.
DF often persists for years. There is sometimes an association with minor trauma, such as insect bites or injections, but this is not always the case.
Dermatofibroma is usually solitary. More than 15 dermatofibromas are described as ‘eruptive dermatofibroma’ and occur in less than 1% of cases. Causes of eruptive DF include immune-mediated diseases.