What is Merkel cell carcinoma?

Merkel cell carcinoma (MCC) is a rare, aggressive type of skin cancer that forms on or just under the skin. It is also called primary small cell carcinoma of the skin, trabecular carcinoma, APUDoma, neuroendocrine carcinoma, endocrine carcinoma, or primary undifferentiated tumor of the skin (). MCC is believed to start in neuroendocrine cells called Merkel cells. These cells release hormones into the blood when stimulated by the nervous system. They migrate from part of the nervous system called the neural crest to the skin (). Merkel cells are believed to play a role in making the skin sensitive to touch ().