Derm Dx: A dark lesion on the thigh - Clinical Advisor

Derm Dx: A dark lesion on the thigh

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The patient is a 62-year-old Caucasian man referred for evaluation of a lesion on his left thigh. The growth has been present about 2 years and is asymptomatic. He has a history of basal carcinoma removed from his nose 1 year ago. Examination reveals a 1.0-cm slightly elevated nodule with dark pigmentation and a somewhat irregular border. Extensive sun damage is noted on his scalp, face, and extremities.

Dermatofibromas are benign fibrohistiocytic tumors that occur most commonly on the lower extremities of women. They range in size from 0.3 cm to greater than 1.0 cm and are usually dome-shaped in appearance, although some manifest depression beneath the skin...

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Dermatofibromas are benign fibrohistiocytic tumors that occur most commonly on the lower extremities of women. They range in size from 0.3 cm to greater than 1.0 cm and are usually dome-shaped in appearance, although some manifest depression beneath the skin surface. Often lateral palpation will result in increased depression, which is referred to as the “dimple” sign. Coloration is variable; most are hyperpigmented, although in lighter-skinned individuals pink to flesh-colored tones are not unusual. It is postulated that minor trauma induces lesion formation. Untreated, dermatofibromas persist for years.

Hemosiderotic variants represent a small subset of dermatofibromas.1 Much of the pigmentation is believed to result from proliferation of macrophages containing hemosiderin.1 Dermoscopy often reveals reddish-blue pigmentation in the center of the lesion, this postulated to arise from extravasation of red blood cells from surrounding vessels.2 As these lesions can resemble melanoma both clinically and dermatoscopically, complete excision is advised.3

Dr. Schleicher is director of the DermDox Center for Dermatology in Hazleton, PA, as well as an associate professor of medicine at the Commonwealth Medical College and a clinical instructor of dermatology for Arcadia University and Kings College.

References

  1. Zaballos P, Llambrich A, Ara M, Olazarán Z, Malvehy J, Puig S. Dermoscopic findings of haemosiderotic and aneurysmal dermatofibroma: report of six patients. Br J Dermatol. 2006;154:244-250.
  2. Ozdemir F, Kilinc I, Akalin T. Homogeneous blue pigmentation in dermatofibroma. J Eur Acad Dermatol Venereol. 2006;20:733-734.
  3. Laureano A, Fernandes C, Cardoso J. Hemosiderotic dermatofibroma: clinical and dermoscopic presentation mimicking melanoma. J Dermatol Case Rep. 2015;9:39-41.
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