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Merkel cell carcinoma (MCC) is a rare skin cancer that develops on sun-exposed skin. Typically, MCC appears as a rapidly growing, painless, bluish to red bump in fair-skinned men over 50 years old. Merkel cell carcinoma is an aggressive skin cancer, often spreading to the lymph nodes and distant organs. In terms of mortality, MCC is second to melanoma for number of skin cancer–related deaths. Other names of the disease include primary cutaneous neuroendocrine carcinoma, small-cell primary cutaneous carcinoma, and cutaneous trabecula carcinoma.
Risk factors for developing MCC include male sex, fair skin, and immunosuppression (a weakening of the immune system either due to disease or medications).
The number of patients diagnosed with Merkel cell carcinoma has increased rapidly over the past few decades because people are getting more sun exposure, there is a growing number of patients with weakened immune systems, and there are now better ways to diagnose the disease.
Merkel cell polyomavirus (MCPyV) has been found in most MCC tumors. It is not known if the virus causes the skin cancer development. It has been proposed that prolonged sun exposure allows the virus to grow. The virus and sun’s rays lead to skin damage, resulting in cancer.
Though MCPyV is associated with MCC, the cancer is not contagious.
A skin biopsy is needed to confirm MCC diagnosis.
Imaging studies may be performed to determine if distant metastasis has occurred.
Patient staging depends on the tumor size, lymph node involvement, and organ metastasis.
The course of treatment for MCC includes surgical removal of the tumor and an associated draining lymph node known as the sentinel node. Additional treatment is needed if metastasis has occurred. Nonsurgical treatments include radiation, chemotherapy, and/or immune-based therapies. New medications can boost the patient’s immune system to destroy tumor cells.
Patients with tumors localized to the skin have the best prognosis. When metastasis occurs, the prognosis is typically poor. New therapies increasing the immune system’s ability to fight cancer cells have shown promising patient outcomes.
Merkel Cell Carcinomahttp://www.merkelcell.org
Skin Cancer Foundationhttp://www.skincancer.org
Published Online: July 31, 2019. doi:10.1001/jamadermatol.2019.2068
Conflict of Interest Disclosures: No disclosures were reported.
Hanlon A. Merkel Cell Carcinoma. JAMA Dermatol. Published online July 31, 2019155(9):1096. doi:10.1001/jamadermatol.2019.2068
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