[Merkel cell carcinoma].

Merkel cell carcinoma (cutaneous neuroendocrine carcinoma) is an uncommon, highly malignant, neuroendocrine skin tumour. Typically, the primary is a fast-growing tough dermal nodule that is characterized histologically by uniform round cells with a small cytoplasmic rim. The tumour cells express the cytokeratins 8, 18, 19, 20, neurofilament, synaptophysin, chromogranin, and neuron-specific enolase. A high frequency of local recurrences (25-77%) and lymph-node metastases (50%) are characteristic features of Merkel cell carcinoma. The 5-year survival rate is 30-74%. Merkel cell carcinomas are highly radiosensitive. Thus, besides surgical methods, radiation should be included into the treatment concept in every stage. We present four cases of Merkel cell carcinoma with different courses for a review-like discussion of this disease giving instructions for rapid diagnosis and effective therapy.