Dermatofibroma, aka cutaneous fibrous histiocytoma, is a benign fibrous nodule composed of fibroblasts and histiocytes. It mainly occurs on the lower extremities. Dermatofibromas are mostly seen in females —although some histological variants are more common among males. Moreover, developing multiple dermatofibromas is usually associated with immunosuppression and autoimmune diseases.
It is unclear whether dermatofibroma arises as a result of a reactive process or a true neoplasm. There still isn’t a well-established cause for this condition. However, minor traumas, such as insect bites and injections are believed to trigger the development of these nodules.
Dermatofibroma characteristically presents as a firm papule/nodule. The size of the nodule varies, it ranges from 5 mm to about 1.5 cm in diameter. The nodule is usually tethered to the skin above it —the skin dimples when pinching the lesion— and mobile over subcutaneous tissue beneath it. The color of the nodule is usually pink or light brown in fair-skinned individuals, and dark brown or black in those with darker skin tones; some nodules may appear paler in the center. Furthermore, dermatofibromas are mainly asymptomatic, but could sometimes be painful, tender, or itchy.
The diagnosis is made clinically, and is supported by dermoscopy. The most common finding on dermoscopy is a central white area surrounded by a faint pigmented network. A diagnostic skin biopsy is only required if there are atypical features; whether clinically or on dermoscopy. These features include a recent enlargement, ulceration, or asymmetrical structures and colors on dermoscopy.
These lesions are benign and harmless, and therefore don’t require any intervention. However, it can be removed surgically if the patient is concerned. Patients should be informed that recurrence is common, as the lesion usually extend beyond the clinical margins. Other modalities, such as cryotherapy and laser rarely showed complete success.
Written by: Rema Aldihan, medical intern.