INTRODUCTION

Malignant melanoma (MM) is the most life-threatening form of skin cancer. It is considered an immunologic tumor and, therefore, raises concerns regarding its behavior and outcomes in the population of immunosuppressed solid organ transplant recipients. Three clinical scenarios are of concern for transplant patients with MM: (1) a history of MM before transplant, (2) development of MM as a result of transmission from the organ donor, and (3) de novo development of MM after transplantation. In making clinical decisions for patients within each scenario, a basic understanding of the pathogenesis of MM, prognostic variables, treatment outcomes, and survival in the general population and transplant population is required.

PATHOGENESIS

Cutaneous melanoma develops from melanocytes that reside in the bottom layer of the epidermis or in nevi extending down into the dermis. Sun exposure, genetic susceptibility with known familial susceptibility genes CDKN2A and CDK4, BRAF gene mutations, and immune response all can have a role in the development of melanoma.

In one early study of MM in renal transplant recipients, a precursor nevus was detected at the margin of the majority of tumor. Additionally, a decreased tumor lymphocytic infiltrate response was present in 10 of 14 tumors. The authors concluded that “MM in renal transplant recipients appears to evolve from precursor nevi in a host unable to mount a tumor-specific cellular immune response.” Although simplistic, the mechanism of pathogenesis proposed on the basis of this study's findings seemed to confirm intuitive ideas.