Case Study : Dermatology
104. Brown spot on back
A 40-year-old man presented to his family physician (FP) with a firm, brown spot on his back.
The patient was unable to see it but his wife had noticed it.
He had no symptoms from the spot and was in otherwise good health.
His father had melanoma of the skin, but survived because it was caught early.
The FP palpated the lesion and found that it was firm, and there was a positive dimple sign when pinched.
He then applied his dermatoscope to the lesion.
The dermatoscope revealed a fine reticular network around a central scar, which confirmed a diagnosis of dermatofibroma.
A dermatofibroma is a benign fibrohistiocytic tumor found in the mid dermis, composed of a mixture of fibroblastic and histiocytic cells.
It represents a fibrous reaction triggered by trauma, a viral infection, or an insect bite.
Many dermatofibromas have a hyperpigmented halo around a central hypopigmented fibrous scar.
Dermoscopy is a very useful diagnostic technique for dermatofibroma.
The most common pattern found is a peripheral reticular pigment network with a central hypopigmented stellate area.
No treatment is necessary unless the diagnosis is uncertain or symptoms warrant it.
Dermatofibromas can be removed using punch excision for small lesions or an elliptical (fusiform) excision down to the subcutaneous fat for larger lesions.
Cryotherapy is one option to shrink the lesion, but the cure rate is low and lesions may regrow.
The patient was relieved that the lesion was not cancer and opted to leave it be, as it was not bothering him.
Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Smith M. Usatine R. Dermatofibroma. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013: 935-939.
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