An Unusual Complete Response to Immunotherapy in a Locoregional Recurrent Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine carcinoma. Multimodal treatment is associated with improved locoregional control and survival outcomes. We present the case of an 80-year-old male patient who developed MCC on the left arm. After surgical resection with clear margins and a negative sentinel lymph node biopsy (SLNB), the patient remained under follow-up. Nine months later, local recurrence with left axillary lymph node involvement was diagnosed. An oncologic multidisciplinary team recommended neoadjuvant nivolumab. After completing six cycles of immunotherapy, a radical resection of the tumor on the left upper limb and a complete left axillary lymph node dissection were performed. The final histopathological report showed scar fibrosis with no residual cancer and no lymph node metastasis. MCC exhibits immunological sensitivity, and the use of immune checkpoint inhibitors has revolutionized the treatment of advanced and recurrent disease.