Aggressive Merkel Cell Carcinoma in a Liver Transplant Recipient

Comment

Transplant recipients represent a well-described cohort of immunosuppressed patients prone to the development of MCC. Merkel cell carcinoma in organ transplant recipients has been most frequently documented to occur after kidney transplantation and less frequently after heart and liver transplantations.^5,6 However, the role of organ type and immunosuppressive regimen is not well characterized in the literature. Clarke et al⁷ investigated the risk for MCC in a large cohort of solid organ transplant recipients based on specific immunosuppression medications. They found a higher risk for MCC in patients who were maintained on cyclosporine, azathioprine, and mTOR (mechanistic target of rapamycin) inhibitors rather than tacrolimus, mycophenolate mofetil, and corticosteroids. In comparison to combination tacrolimus–mycophenolate mofetil, cyclosporine-azathioprine was associated with an increased incidence of MCC; this risk rose remarkably in patients who resided in geographic locations with a higher average of UV exposure. The authors suggested that UV radiation and immunosuppression-induced DNA damage may be synergistic in the development of MCC.⁷

Merkel cell carcinoma most frequently occurs on sun-exposed sites, including the face, head, and neck (55%); upper and lower extremities (40%); and truncal regions (5%).⁸ However, case reports highlight MCC arising in atypical locations such as the buttocks and gluteal region in organ transplant recipients.^7,9 In the general population, MCC predominantly arises in elderly patients (ie, >70 years), but it is more likely to present at an earlier age in transplant recipients.^6,10 In a retrospective analysis of 41 solid organ transplant recipients, 12 were diagnosed before the age of 50 years.⁶ Data from the US Scientific Registry of Transplant Recipients showed a median age at diagnosis of 62 years, with the highest incidence occurring 10 or more years after transplantation.⁷

Merkel cell carcinoma behaves aggressively and is the most common cause of skin cancer death after melanoma.¹¹ Organ transplant recipients with MCC have a worse prognosis than MCC patients who are not transplant recipients. In a retrospective registry analysis of 45 de novo cases, Buell at al⁵ found a 60% mortality rate in transplant recipients, almost double the 33% mortality rate of the general population. Furthermore, Arron et al¹⁰ revealed substantially increased rates of disease progression and decreased rates of disease-specific and overall survival in solid organ transplant recipients on immunosuppression compared to immunocompetent controls. The most important factor for poor prognosis is the presence of lymph node invasion, which lowers survival rate.¹²

Conclusion

Merkel cell carcinoma following liver transplantation is not well described in the literature. We highlight a case of an aggressive MCC arising in a sun-protected site with rapid metastasis 6 years after liver transplantation. This case emphasizes the importance of surveillance for cutaneous malignancy in solid organ transplant recipients.