Dermatology
AKT · Dermatology/Benign lesionslow yield
Dermatofibroma
Benign fibrohistiocytic dermal nodule
Overview
A common benign fibrous dermal nodule, often on the legs of women, frequently following minor trauma or an insect bite. The diagnostic test is the DIMPLE (Fitzpatrick) sign — lateral pinching causes the lesion to dimple inward.
Recognise
- Firm, well-defined, 5–10 mm dermal papule/nodule, usually pigmented brown and often on the lower legs
- Positive dimple sign — pinching the skin laterally tethers and dimples the lesion downward
- Often a history of preceding minor trauma/insect bite; usually asymptomatic
Red flags
- Rapid growth, large size, or unusual features → consider dermatofibrosarcoma protuberans (biopsy)
Differentials & how to tell them apart
Melanocytic naevussoft melanocytic mole, no dimple sign
Malignant melanomaasymmetric, changing pigment — a firm fibrous dermatofibroma with a dimple sign is benign
Dermatofibrosarcoma protuberansa firm plaque/nodule that grows — biopsy if atypical/enlarging
Clinical image
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Investigations
Clinical (the dimple sign). Excision/biopsy if diagnosis uncertain or growing.
Management
Reassurance; excise only for diagnostic doubt or symptoms
- 1Reassure — a firm dermal nodule with a positive dimple sign on the leg is a benign dermatofibroma.Gate: The dimple (Fitzpatrick) sign confirms a benign dermatofibroma — but a rapidly growing or atypical "dermatofibroma" should be biopsied to exclude dermatofibrosarcoma protuberans
- 2Excision if symptomatic, uncertain, or for cosmesis.
Reassurance — benign; usually left alone
Excision — for diagnostic doubt, symptoms, or cosmesis
Key points
The dimple sign is the classic bedside test. They commonly follow an insect bite and may darken over time but remain benign.
Monitor & prognosis
Stability; review if it grows.
Benign and stable.
Source: DermNet; StatPearls