Long lasting complete regression of a metastatic polyomavirus-positive Merkel cell carcinoma after COVID-19 booster vaccination

Merkel cell carcinoma (MCC) is a rare but highly aggressive primary cutaneous neuroendocrine cancer whose incidence is increasing worldwide. MCC represents the second leading cause of skin cancer death after melanoma [1,2]. It typically manifests as a red nodule or plaque with fast growth, most commonly on sun exposed areas [3]. Risk factors include fair skin type, advanced age, ultraviolet radiation exposure, male sex, immunosuppression, and integration of Merkel cell polyomavirus DNA (MCPyV) into the host genome [3].