How would you manage a Merkel cell carcinoma that spontaneously regressed clinically in a patient medically high-risk for surgical resection/anesthesia?  

Less than 5% of MCCs are T0. I’ve never seen spontaneous regression of a biopsy-proven MCC in over 45 years. That said, should lightning strike, RT to the primary site and elective RT to the regional nodes. 

“Spontaneous regression” of Merkel cell carcinoma has been studied in a limited capacity. I don’t know of any studies that clearly guide management. Patients who present with an unknown primary Merkel cell carcinoma and regional lymphadenopathy probably have a regressed primar...