Merkel cell carcinoma.

Merkel cell carcinoma is a rare malignant neoplasm of the skin which is locally invasive and frequently metastasizes to lymph nodes, liver, lungs, bone, and brain. Computed tomographic and pathologic findings in an elderly woman with Merkel cell carcinoma of the buttock and regional nodal metastasis are reported. The presence of calcitonin and neuron-specific enolase within the tumor supports the theory that Merkel cell carcinoma is a neuroendocrine tumor derived from the APUD (amine precursor uptake and decarboxylase) system.