Adjuvant Radiotherapy for Dissected Parotid Lymph Nodes Containing Merkel Cell Carcinoma from an Unknown Primary Skin Site: 2 Case Reports.

BACKGROUND Merkel cell carcinoma (MCC) is an aggressive neuroendocrine malignancy that has increased in incidence in recent decades. The management of MCC should involve multidisciplinary experts to achieve optimal patient outcomes. Radiotherapy is commonly used as adjuvant therapy. Our literature review of MCC indicates that aggressive adjuvant radiotherapy might have a positive impact on overall local control and survival. CASE REPORT The first case is a 75-year-old male patient who discovered a right preauricular mass 2 weeks prior. He underwent right parotidectomy with tumor removal on 2012/07/09, and pathology revealed MCC in 3 lymph nodes. The patient received postoperative adjuvant radiotherapy (61.2 Gy) to the remaining right parotid tumor bed and right neck lymph nodes. The patient refused adjuvant chemotherapy. During long-term follow-up, the patient remained disease free for 10 years. The other case is a 73-year-old female patient with metastatic MCC in a left parotid lymph node. She also underwent left parotidectomy with tumor removal, and pathological staging performed according to the 8th edition of the AJCC staging system showed pTxN1aMx, stage IIIA. After the operation, she received postoperative adjuvant radiotherapy (56 Gy) to the remaining left parotid and left neck lymph nodes. The patient remained disease free for 14 months. CONCLUSIONS Metastatic MCC of the parotid lymph nodes without a detectable primary skin tumor is very rare. Adjuvant radiotherapy to the tumor bed and regional nodal basin might be beneficial for preventing disease recurrence despite the absence of systemic medical therapy.