Background: Although there are reports of squamous cell carcinoma arising within and adjacent to Merkel cell carcinoma, and one report of an atypical fibroxanthoma-like tumor arising in an irradiated recurrent Merkel cell carcinoma, there have previously been no reports of an immunohistochemically verified atypical fibroxanthoma occurring in conjunction with a Merkel cell carcinoma. Objective: We report on a neoplasm with distinct features of both Merkel cell carcinoma and atypical fibroxanthoma. Methods: Histologic and immunohistochemical evaluations were performed. Results: Our results verify the finding of a combined Merkel cell carcinoma and atypical fibroxanthoma. Conclusion: This case is an interesting and unusual combination of tumors. The origin of the Merkel cell carcinoma is revisited. Debated origins include neuroendocrine, epithelial, and pleuripotent stem cell.
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