Macrophage‐rich epithelioid angiosarcoma mimicking malignant melanoma

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Abstract
Background:  Cutaneous epithelioid angiosarcoma is a type of cutaneous angiosarcoma and usually arise both on the head or neck of the elderly.Case report:  An 86‐year‐old male with an epithelioid angiosarcoma of the scalp that mimicked malignant melanoma.Results:  A large irregular dark grey‐blue plaque with an adjacent speckled tan nodule was suggestive of a primary cutaneous malignant melanoma with adjacent in‐transit metastasis. Both had a well‐circumscribed growth pattern and were composed of numerous large epithelioid cells with scattered severe atypia and mitoses. The tumor was positive for S‐100 protein and vimentin and negative for low‐ and high‐molecular weight cytokeratins. However, at high power, the epithelioid cells with severe atypia were negative for S‐100 protein, and abundant large epithelioid macrophages were responsible for the S‐100 protein positivity. The malignant tumor cells were negative for HMB‐45, positive for CD31 and Factor VIII‐related antigen, and focally positive for CD34. A focus of infiltrative, classical angiosarcoma with irregular vascular channels lined with plump, anaplastic endothelial cells was then found deep to the epithelioid tumor.Conclusions:  Macrophage‐rich epithelioid angiosarcoma demonstrates abundant S‐100 protein‐positive epithelioid macrophages. This subset of epithelioid angiosarcoma may mimic malignant melanoma and may present as a pitfall in diagnosis.

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