Merkel Cell Carcinoma of the Gluteal Region with Ipsilateral Metastasis into the Pancreatic Graft of a Patient after Combined Kidney-Pancreas Transplantation

Background: Merkel cell carcinoma (MCC) is a rare tumour of the skin that predominantly affects elderly or immunocompromised patients. The malignant transformation of Merkel cells is currently considered to be related to an infection with Merkel cell polyomavirus. Case Report: We present the case of a 62-year-old man who developed a Merkel cell polyomavirus-positive MCC in a non-UV-exposed part of the right gluteal region 8 years after combined kidney-pancreas transplantation. Following excision and radical re-excision of the tumour, no adjuvant radiotherapy was indicated because of the risk of adjacent pancreatic graft failure. Despite adjustment of the immunosuppressive therapy with conversion to sirolimus, the tumour generalised and metastasised into the pancreatic graft, leading to its failure. Subsequent chemotherapy did not affect the course of the disease, and the patient died 9 months after diagnosis. Conclusions: To our knowledge, we present the first case of MCC associated with metastatic involvement of the transplanted pancreas followed by its subsequent failure. Given the highly aggressive course of the disease in patients after organ transplantation, MCC therapy should be sufficiently aggressive from the time of diagnosis and should not be influenced by attempts to preserve graft function.