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Merkel cell carcinoma (MCC) usually starts on areas of skin exposed to the sun, especially the face, neck, arms, and legs, but it can occur anywhere on the body.
The first sign of Merkel cell carcinoma is often a single pink, red, or purple shiny bump that usually doesn't hurt. Sometimes the skin on the top of the tumor breaks open and bleeds.
These tumors tend to grow quickly. They might spread as new lumps in the nearby skin. They might also reach nearby lymph nodes (small collections of immune system cells throughout the body). Over time, the lymph nodes might grow large enough to be seen or felt as lumps under the skin (usually in the neck or under the arm).
Merkel cell carcinoma is rare, and it can look like many other, more common types of skin cancer or other skin problems when it first appears. Because of this, doctors might not suspect MCC at first, and the diagnosis is often made only after the tumor is biopsied.
It’s very important to have any new, growing, or changing lumps, bumps, or spots on your skin checked by a doctor as soon as possible, so that the cause can be found and treated, if needed. The earlier any type of skin cancer is found, the easier it’s likely to be to treat it.
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
National Cancer Institute. Merkel Cell Carcinoma Treatment (PDQ)–Health Professional Version. 2024. Accessed at https://www.cancer.gov/types/skin/hp/merkel-cell-treatment-pdq on November 18, 2024.
Tai P, Nghiem PT, Park SY. Pathogenesis, clinical features, and diagnosis of Merkel cell (neuroendocrine) carcinoma. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/pathogenesis-clinical-features-and-diagnosis-of-merkel-cell-neuroendocrine-carcinoma on November 18, 2024.
Xu YG, Aylward JL, Swanson AM, et al. Chapter 67: Nonmelanoma Skin Cancers. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa. Elsevier: 2019.
Last Revised: January 10, 2025
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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