[Merkel cell carcinoma: report of three cases]

Merkel cell carcinoma is a primary cutaneous neuroendocrine carcinoma occurring commonly in the head and neck of middle-aged and elderly patients. While not very rare, this disease has never been reported in Taiwan. We report the clinical and pathologic features of three patients with Merkel cell carcinoma. The patients included one male (aged 56) and two females (aged 70, 80). The primary sites of the tumors were the hand in one patient and the head and neck in two. Two patients had regional lymph node metastasis. Case 1 had concurrent chronic arsenicalism with multiple Bowen's disease and squamous cell carcinoma of the skin. Histopathology revealed tumor cell infiltration throughout the dermis. In two cases, the tumor cells were small, round and non-cohesive, like lymphocytic infiltrates. In Case 3, however, they were large, oval and formed in nests. The tumor cells were keratin (AE1), neuron-specific enolase and chromogranin positive by immunohistochemical staining. Electronmicroscopy in Case 1 revealed a few cytoplasmic intermediate filaments and neurosecretory granules. Therapy consisted of radiation in 2 patients and surgery in 1; one died during radiotherapy, the other two survived and showed no signs of recurrence at 10 and 21 months.