Merkel cell carcinomas are uncommon, but aggressive, cutaneous malignancies of neuroendocrine differentiation. To the pathologist, these lesions appear as sheets of undifferentiated tumor cells with little cytoplasm and dense nuclear chromatin. They are members of the group of "small round blue cell tumors," which includes small cell carcinomas of the lung, lymphomas, and neuroblastomas. Analogous to other skin malignancies, Merkel cell carcinomas frequently arise in the head and neck region and are commonly found in the elderly population. Merkel cell carcinomas have a high propensity for regional and distant metastases, and recurrences are frequently seen. Surgical excision is the recommended first-line treatment followed by adjuvant radiation therapy. Because of the high incidence of occult regional metastasis, patients with clinical and radioghaphically negative necks should undergo elective dissection, irradiation, or preferably sentinel lymph node biopsy.
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