Hemosiderotic Dermatofibroma: A Rare and Atypical Variant Capable of Clinically Resembling Melanoma.

A dermatofibroma (DF) is a common, benign tumor composed of fibroblastic and histiocytic cells. DF presents clinically with several different reported variants. One rare variant is hemosiderotic DF (HDF), which is made up of small blood vessels and hemosiderin deposits. HDF can be indistinguishable, clinically, from melanoma, making the use of other pathological tools crucial in the diagnosis. We report the case of a 25-year-old male medical student from the Caribbean who presented to our clinic with a single asymptomatic pigmented cystic lesion on his left posterior calf. The cystic lesion was excised surgically. Histopathology examination of the excised mass revealed a moderately cellular, poorly demarcated, dermal, fibrohistiocytic proliferation. Pathology consultation confirmed a diagnosis of HDF.