Introduction

Merkel cell carcinoma is a rare, fast-growing cancer that usually appears as a flesh-colored or bluish-red nodule on your skin, often on your face, head or neck. Merkel cell carcinoma tends to spread quickly (metastasize) to other parts of your body. Like other types of skin cancers, the incidence of Merkel cell carcinoma is increasing worldwide.

Merkel cell carcinoma, also called neuroendocrine carcinoma of the skin, most often develops in older people. Long-term sun exposure or having a weak immune system may increase your risk of developing Merkel cell carcinoma.

The type of treatment you’ll undergo depends on whether the cancer has spread beyond your skin by the time it’s diagnosed.

Signs and symptoms

The first sign of Merkel cell carcinoma is a fast-growing, painless nodule (tumor) on your skin. The shiny nodule may be skin colored or may appear in shades of red, blue or purple. Nearly half of Merkel cell carcinomas appear on the face, head or neck, but they can develop anywhere on your body, even on areas not exposed to sunlight.

If the skin cancer has spread to other parts of your body, you may experience swollen lymph nodes, pain or fatigue.

Causes

Merkel cell carcinoma is named after Merkel cells, which are found at the base of the outermost layer of your skin (epidermis). Merkel cells may be associated with the sense of touch.

It’s not certain what causes Merkel cell carcinoma to develop. One theory is that Merkel cell carcinoma may arise from the Merkel cell. Or it may be that certain immature cells (skin stem cells) become cancerous and develop features that make them look like Merkel cells.

Researchers have detected a number of genetic abnormalities in Merkel cell carcinoma cells. However, it’s not known how these genetic changes affect cancer development.