Merkel Cell Carcinoma
Merkel cell carcinomas arise predominantly in sun-exposed skin in the elderly. Histologically, they show a trabecular, intermediate, or small cell pattern and can be difficult to differentiate from metastatic small cell carcinoma or lymphoma. On EM, neuroendocrine granules can be demonstrated. The prognosis is poor due to frequent metastases. The cells of origin are neuroendocrine cells found in the basal epidermal layer, hair follicles, and oral mucosa.