[Merkel cell carcinoma--clinically often misjudged].

Merkel cell carcinoma is a rare, rapidly growing, highly malignant dermal tumor which occurs preferentially on light-exposed skin in advanced age. The course of the disease is frequently characterized by the occurrence of lymph node metastases and local recurrences, even in the first year after removal of the primary tumour. The five-year overall survival rate is only about 65 %, despite rigorous therapy. The histological pattern is characterized by trabecular strands of small, uniform cells with large basophilic nuclei and typical neuroendocrine granules. The diagnosis is confirmed immunohistochemically by neuroendocrine and epithelial markers. The excision of the primary tumor is regarded as first-line therapy. Adjuvant radiatiotherapy is almost always indicated and should also include lymph node drainage. In the stage of nodal disease, a combination of excision and radiotherapy is recommended. Adjuvant chemotherapy can be applied in this stage, as in small-cell bronchial carcinoma. The prognostic advantage has, however, not been proven. Despite good response to radiatiotherapy and chemotherapy, with at least prolonged recurrence-free intervals, Merkel cell carcinoma is rarely curable at the distant metastasizing stage. Individually defined, aggressive treatment,including radiatiotherapy, may in future considerably improve the prognosis, especially in the early stages of the disease.