Mast cells and vascular density have prognostic value in Merkel cell carcinoma

Abstract

IntroductionThe authors present a form of dermatofibroma rarely seen and described, with a clinical appearance of giant plaques accompanied by satellite lesions.Case reports Unusual giant dermatofibromata are reported in a 40-year-old man and a 48-year-old man, who both presented with plaques on a lower limb. The largest plaque in each case was well-defined, reddish brown, indurated and measured 50 mm ¥ 30 mm and 70 mm ¥ 40 mm, respectively. Several satellite lesions were present around the large plaques. Dermoscopic examination showed diffuse homogenous pigmentation in the absence of other diagnostic criteria for dermatofibroma.Histology Light microscopy of biopsies from each patient displayed dermal proliferation of fibrohistiocytic cells, with a storiform dermal proliferation of spindle cells of bland appearance, and entrapped intervening collagen bundles. The overlying epidermis was acanthotic and there was no evidence of malignancy. Immunohistochemical staining was positive for Factor XIIIa and negative for CD34. Based on the histological findings, a diagnosis of giant dermatofibroma was made for each of these cases. ConclusionThese cases represent extraordinary examples of giant dermatofibroma as the lesions were not pedunculated as reported in previous cases, 1,2 and also exhibited the uncommon feature of satellitosis. Fewer than 20 cases of giant dermatofibroma have been reported to date, and only one, which was histologically different to the present cases, has shown satellitosis and a plaque-like appearance. 3 The authors propose the term 'Plaque-like Dermatofibroma with Satellitosis' for this distinct clinical entity.