Multiple Merkel cell carcinomas: Late metastasis or multiple primary tumors? A molecular study

aCGH: array comparative genomic hybridization FFPE: formalin-fixed paraffin-embedded MCC: Merkel cell carcinoma MCpV: Merkel cell polyomavirus PET/CT: positron emission tomography/ computed tomography SLNB: sentinel lymph node biopsy INTRODUCTION In the United States, the incidence and mortality rates for Merkel cell carcinoma (MCC) have more than tripled in the last 2 decades. The main risk factors involved in MCC pathogenesis include ultraviolet light exposure, immunosuppression, and Merkel cell polyomavirus (MCpV). The most common sites include the head and neck (53%) and extremities (34%e35%), with trunk and mucosal surfaces representing less than 10% of cases. MCC has a high propensity for local recurrence, with a median time between diagnosis and recurrence of 6 months. We present a case of a 79-year-old woman who initially presented with 2 MCCs of the nasal bridge and left arm, followed by a third MCC on the right nose 8 years later. We used array comparative genomic hybridization (aCGH) testing to determine whether the most recent tumor was the result of metastasis or represented a delayed primary recurrence of MCC. Through this case, we suggest that using aCGH to distinguish between primary and metastatic disease can play an important role in future MCC management.