Merkel cells are normal cells in the epidermis Epidermis The skin is the body’s largest organ. It serves many important functions, including Protecting the body against trauma Regulating body temperature Maintaining water and electrolyte balance Sensing... read more 
(the outer layer of the skin). These cells mostly function as touch receptors and they produce certain hormones. Merkel cell carcinoma arises from uncontrolled growth of cells in the skin that share some characteristics with normal Merkel cells.
Merkel cell carcinoma is diagnosed at an average age of 75. Merkel call carcinoma also affects younger people whose immune system is weakened. Sun exposure increases the risk, as does having another cancer. The Merkel cell polyomavirus may be a contributory factor. This cancer commonly spreads to the lymph nodes.
Symptoms of Merkel Cell Carcinoma
The cancer is typically a firm, shiny, flesh-colored or bluish red bump. Cancers tend to grow rapidly without causing pain or tenderness. Although Merkel cell carcinoma can affect any part of the skin, it is most common on skin that has been chronically exposed to sunlight (for example, the face and arms).
Diagnosis of Merkel Cell Carcinoma
Biopsy
A biopsy Biopsy Doctors can identify many skin disorders simply by looking at the skin. A full skin examination includes examination of the scalp, nails, and mucous membranes. Sometimes the doctor uses a hand-held... read more 
is done to confirm the diagnosis of Merkel cell carcinoma. During this procedure, a small piece of skin is removed and examined under a microscope.
In most people, the cancer has already spread by the time the diagnosis has been made, so the prognosis for Merkel cell carcinoma is poor.
Prevention of Merkel Cell Carcinoma
Because Merkel cell carcinoma can be caused by sun exposure Overview of Sunlight and Skin Damage Sunlight stimulates vitamin D production, helps control some chronic skin diseases (such as psoriasis), and causes a sense of well-being. However, sunlight can cause skin damage. Damage includes... read more 
, people can help prevent this cancer by doing the following:
Avoiding the sun Avoidance Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more
: For example, seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when the sun’s rays are strongest), and avoiding sunbathing and the use of tanning bedsWearing protective clothing Clothing Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more
: For example, long-sleeved shirts, pants, and broad-brimmed hatsUsing sunscreen Sunscreens Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more
: At least sun protection factor (SPF) 30 with UVA and UVB protection used as directed and reapplied every 2 hours and after swimming or sweating but not used to prolong sun exposure
Treatment of Merkel Cell Carcinoma
Surgical removal of the tumor
Usually radiation therapy and removal of lymph nodes
Sometimes chemotherapy
Treatment of Merkel cell carcinoma usually involves surgery to remove the tumor, often followed by radiation therapy Radiation Therapy for Cancer Radiation is a form of intense energy generated by a radioactive substance, such as cobalt, or by specialized equipment, such as an atomic particle (linear) accelerator. Radiation preferentially... read more , removal or biopsy of lymph nodes, or both.
If cancer has spread or returns, chemotherapy Chemotherapy and Other Systemic Cancer Treatments Systemic treatments are those that have effects throughout the body rather than being applied directly to the cancer. Chemotherapy is a form of systemic treatment that uses drugs to kill cancer... read more may be recommended.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Merkelcell.org: A resource to help people find access to Merkel cell specialists and other patient resources
American Cancer Society: Merkel Cell Skin Cancer: Information about Merkel cell carcinoma, including detection, prevention, treatment options, and other resources
The Skin Cancer Foundation: Merkel Cell Carcinoma: Information about Merkel cell carcinoma, including detection, prevention, treatment options, and other resources
