INTRODUCTION

Merkel cell carcinoma (MCC) is a neuroendocrine carcinoma of the skin that has a higher mortality (approximately 33% at three years) than melanoma in the general population. The fact that 8% of MCC cases have been encountered in solid organ transplant recipients (OTRs) indicates a greater than tenfold increased incidence among these patients. This increased risk among transplant patients and a 60% disease-specific mortality of MCC in this population make it an important issue in transplant medicine. Further challenges surrounding MCC include a therapeutic approach that is very different than that employed for other skin cancers, is controversial within the literature, and that is in a state of evolution. Optimal care of MCC in OTRs requires coordination between dermatologists, surgeons, transplant physicians, and radiation and medical oncologists.

Compared to most other malignant processes, MCC has a relatively recent history dating to only 1972 when Toker described five cases of “trabecular cell carcinoma of the skin.” The histologic diagnosis of this cancer was difficult until 1978 when Tang and Toker described “dense core granules” on electron microscopy in these tumors. In 1992, a major additional development was the description of antibodies that could detect cytokeratin 20, which is specific for MCC relative to other malignant processes. This new immunohistochemical technique made the diagnosis of MCC much more straightforward. Over the past fifteen years, there has been evidence of rapidly increasing incidence of MCC.