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An Unusual Case of Merkel Cell Carcinoma Metastasis to the Kidneys

By: Julia Fiederlein
Posted: Wednesday, July 14, 2021

Merkel cell carcinoma frequently metastasizes to the lymph nodes, lungs, liver, and bones. However, an unusual case, which localized in the kidney, was described by Ibrahim Boukhannous, MD, of the Mohamed I University, Oujda, Morocco, and colleagues in the journal Urology Case Reports.

A 49-year-old man presented with an asymptomatic subcutaneous nodule on the left buttock, and he underwent cutaneous resection; adjuvant radiotherapy was not administered after surgery. An immunohistochemistry test showed positivity of neuroendocrine markers, such as CK20, chromogranine A, synaptophysine, and negativity of PS100 and CK7; thus, the patient was diagnosed with Merkel cell carcinoma. He underwent a thoracic abdominopelvic scan after experiencing pain in the left lumbar fossa. This scan revealed a tumor in the mid part of the left kidney cortex with endo and exo renal development, rupture of the external cortex, contrasting heterogeneously, and magma of lymphadenopathy in the left lumbar-aortic region.

The patient underwent an enlarged total left nephrectomy, which showed a proliferation infiltrating the renal hilum. A renal tumor proliferation arranged in neuroendocrine clusters made of cells with scarce cytoplasm was identified by histopathologic examination; the tumor stroma was fibrocongestive, with the presence of juxtatumoral carcinomatous emboli. Tumor cells were found to be immunohistochemically positive for CK20 and negative for PS100. Based on these results, renal metastasis of the Merkel cell cutaneous carcinoma was diagnosed. The patient was lost to follow up after being referred to an oncology center.

Disclosure: No information regarding conflicts of interest was provided.

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