<p id="par0005">There are only two cases reported in the literature Merkel cell carcinoma in the retroperitoneum.p>
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<p id="par0010">The most plausible theory is the retroperitoneal mass could be a massively enlarged lymph node where precursor cells became neoplastic.p>
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<p id="par0015">The less probable theory is the non-described “regression” phenomena of a cutaneous MCC, but we are not found a primary skin lesion.p>
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<p id="par0020">Preoperative chemotherapy and excision of the primary tumor is the surgical treatment of choice for retroperitoneal MCC.p>