Merkel cell carcinoma: a diagnostic and therapeutic challenge

Merkel cell carcinoma (cutaneous neuroendocrine carcinoma) is a highly mali gnant, neuroendocrine skin tumor. It mostly occurs in elderly patients in t he sun-exposed skin of the head and neck and the extremities. Merkel cell c arcinomas develop as fast-growing dermal tumors. They are characterized by a high frequency of lymph-node metastases (50%) and local recurrences (25-7 7%). The 5-year survival rate is 30-74%. Histology reveals uniform, round c ells with a small cytoplasmic rim expressing cytokeratin 20, neurofilament, synaptophysin, chromogranin, and neuron-specific enolase. Ultrastructurall y, 100-200 nn electron dense granules are typical findings. Wide surgical e xcision, followed by radiotherapy, is the treatment of choice. Regional lym ph-node metastases should be treated by radical lymph-node excision and rad iotherapy. In advanced metastatic Merkel cell carcinoma, a remission can be achieved by different chemotherapy schedules or the somatostatin analogue octreotide. However, the prognosis remains poor. The current knowledge abou t this disease and guidelines for effective diagnosis and treatment are giv en.