Merkel cell carcinoma is a very rare disease in which malignant (cancer) cells form in the skin.
Merkel cells are found in the top layer of the skin. These cells are very close to the nerve endings that receive the sensation of touch. Merkel cell carcinoma, also called neuroendocrine carcinoma of the skin or trabecular cancer, is a very rare type of skin cancer that forms when Merkel cells grow out of control. Merkel cell carcinoma starts most often in areas of skin exposed to the sun, especially the head and neck, as well as the arms, legs, and trunk.
Anatomy of the skin, showing the epidermis, dermis, and subcutaneous tissue. Merkel cells are in the layer of basal cells at the deepest part of the epidermis and are connected to nerves.
Merkel cell carcinoma tends to grow quickly and to metastasize (spread) at an early stage. It usually spreads first to nearby lymph nodes and then may spread to lymph nodes or skin in distant parts of the body, lungs, brain, bones, or other organs.
Sun exposure and having a weak immune system can affect the risk of Merkel cell carcinoma.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk with your doctor if you think you may be at risk. Risk factors for Merkel cell carcinoma include the following:
- Being exposed to a lot of natural sunlight.
- Being exposed to artificial sunlight, such as from tanning beds or psoralen and ultraviolet A (PUVA) therapy for psoriasis.
- Having an immune system weakened by disease, such as chronic lymphocytic leukemia or HIV infection.
- Taking drugs that make the immune system less active, such as after an organ transplant.
- Having a history of other types of cancer.
- Being older than 50 years, male, or white.
Merkel cell carcinoma usually appears as a single painless lump on sun-exposed skin.
This and other changes in the skin may be caused by Merkel cell carcinoma. Other conditions may cause the same symptoms. Check with your doctor if you see changes in your skin.