Merkel Cell Carcinoma

Merkel cell carcinoma, also known as cutaneous APUDoma, primary neuroendocrine carcinoma of the skin, primary small cell carcinoma of the skin, and trabecular carcinoma of the skin ), is a rare and highly aggressive cancer in which malignant cancer cells develop in hair follicles, or on or beneath the skin.

The majority of Merkel cell carcinomas appear to be caused in part by a virus, which has been named Merkel cell polyomavirus (MCV). Direct evidence for this oncogenetic mechanism comes from research showing that inhibition of production of MCV proteins causes MCV-infected Merkel carcinoma cells to die but has no effect on malignant Merkel cells that are not infected with this virus. MCV-uninfected tumors, which account for approximately 20% of Merkel cell carcinomas, appear to have a separate and as-yet unknown cause.

This cancer is considered to be a form of neuroendocrine tumor. While patients with a small tumor (less than 2 cm) that has not yet metastasized to regional lymph nodes have an expected 5-year survival rate of more than 80 percent, once a lesion has metastasized regionally, the rate drops to about 50 percent. Up to half of patients that have been seemingly treated successfully (i.e. that initially appear cancer-free) subsequently suffer a recurrence of their disease. Recent reviews cite an overall 5-year survival rate of about 60% for all MCC combined.

Merkel cell carcinoma (MCC) occurs most often on the sun-exposed face, head, and neck.