Clinicopathological characteristics and prognosis of Merkel cell carcinoma: a single-center retrospective study in Korea

Background Merkel cell carcinoma (MCC) is an aggressive neuroendocrine tumor of the skin with high mortality. However, its clinical characteristics in Asian patients remain uncertain owing to its low incidence. Objective To analyze the clinicopathological features of MCC and identify factors associated with its prognosis. Methods The medical records of 62 patients with MCC were retrospectively reviewed. Data on clinical features, survival outcomes, prognostic factors, histopathology and immunohistochemical profile of the patients were collected and analyzed. Merkel cell polyomavirus status was evaluated using immunohistochemistry. Results The incidence of MCC significantly increased over time. The mean duration of follow-up was 51.2 months, with an overall 5-year survival of 80.6%. More female patients with MCC were identified than male patients (1.3:1). Approximately half of the patients had stage I disease at the time of initial presentation. The primary tumor was frequently located in the lower extremities (40.3%), followed by the head and neck (32.3%), upper extremities (22.6%), and the trunk (4.8%). Male sex was associated with poorer overall survival ( p = 0.003). Post-resection adjuvant radiotherapy significantly improved the overall survival ( p = 0.023). Sentinel lymph node biopsy during surgery ameliorated the progression-free survival ( p = 0.036) in patients with stage I or II cancer. Lymphovascular and perineural invasion were associated with a poor prognosis. Old age, immunohistochemical profiles, and Merkel cell polyomavirus-positivity were not associated with prognosis. Conclusion Post-surgical adjuvant radiotherapy and sentinel lymph node biopsy significantly improve the course of MCC.