Dermatofibroma

Latest update 16/06/09

Aetiology

• A dermatofibroma is a benign skin lesion. The exact aetiology is uncertain - some believe it to represent a traumatic reaction such as to an insect bite, others believe it is a true neoplasm

Key diagnostic features

• Age of presentation - Young adults most commonly affected
• Sex - Woman more than men
• Distribution - Commonly on the limbs, especially the thighs and lower legs. Multiple lesions are often found
• Appearance
  • Most lesions are approximately 5mm in size and slightly elevated
  • Palpation reveals that much of the lesion sits deep to the skin surface and has a firm consistency
  • Pinching the lesion results in central dimpling
  • Some lesions are larger and much more nodular in appearance
  • Colour tends be red - brown. A deeper area of pigmentation can be found at the periphery of the lesion

Dermoscopic appearance

• The appearance of a central scar-like white area associated with a very fine peripheral pigment network is very characteristic. The holes formed by the network tend to be more rounded as opposed to the shapes seen in melanocytic lesions which are more angulated
• Early/flat lesions may have little in the way of a central white area

Treatment

• Dermatofibroma do not normally require treament
• Lesions are occasionally removed in cases of diagnsotic uncertainty, and in some patients who request removal as a result of the lesion feeling uncomfortable
• Treatment is by surgical excision

	Figure 1 – Dermatofibroma of the shin Note the brown pigment at the periphery
	Figure 2 – Dermatofibroma The shiny appearance is an alcohol based gel used to aid dermoscopy
	Figure 3 – Dermoscopic appea rance of figure 2 Note the white centre and fine brown peripheral network (arrow)
	Figure 4 - Dermatofibroma
	Figure 5 – Dermoscopic appearance of figure 4 Lesion demonstrates faint peripheral pigment network (arrow)
	Figure 6 – Dermatofibroma on the arm Much more nodular
	Figure 7 – Side view of figure 6
	Figure 8 – A very flat dermatofibroma Palpation revealed a firm lesion sitting under the surface of the skin
	Figure 9 – Dermatofibroma of the waist An uncommon site, but dermatofibroma can affect any body site. Note the denser pigment at the periphery
	Figure 10 – Dermatofibroma This lesion was not typical of a dermatofibroma and needed excising for diagnostic reasons. Histology showed a dermatofibroma
	Figure 11 – Dermoscopic appearance of figure 10
	Figure 12 - Dermatofibroma in a dark-skinned patient
	Figure 13 - Dermoscopic appearance of figure 12 The same features exist as in patients with lighter skin - a central pale area and a fine peripheral pigment network
	Figure 14 - Close-up of above