Merkel cell carcinoma is a rare type of skin cancer that usually appears as a flesh-colored or bluish-red nodule, often on your face, head or neck. Merkel cell carcinoma is also called neuroendocrine carcinoma of the skin.

Merkel cell carcinoma most often develops in older people. Long-term sun exposure or a weak immune system may increase your risk of developing Merkel cell carcinoma.

Merkel cell carcinoma tends to grow fast and to spread quickly to other parts of your body. Treatment options for Merkel cell carcinoma often depend on whether the cancer has spread beyond the skin.

Source: http://www.mayoclinic.com

The first sign of Merkel cell carcinoma is usually a fast-growing, painless nodule (tumor) on your skin. The nodule may be skin colored or may appear in shades of red, blue or purple. Most 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.

When to see a doctor

If you notice a mole, freckle or bump that is changing in size, shape or color, growing rapidly or bleeding easily after minor trauma, such as washing your skin or shaving, make an appointment with your doctor.

Source: http://www.mayoclinic.com

It's not clear what causes Merkel cell carcinoma. Merkel cell carcinoma begins in the Merkel cells. Merkel cells are found at the base of the outermost layer of your skin (epidermis). Merkel cells are connected to the nerve endings in the skin that are responsible for the sense of touch.

Source: http://www.mayoclinic.com

Tests and procedures used to diagnose Merkel cell carcinoma include:

• Physical exam. Your doctor will examine your skin for unusual moles, freckles, pigmented spots and other growths.
• Removing a sample of suspicious skin. During a procedure called a skin biopsy, your doctor removes the tumor or a sample of the tumor from your skin. The sample is analyzed in a laboratory to look for signs of cancer.

Determining the extent

Your doctor may use the following tests to help determine whether the cancer has spread beyond your skin:

• Sentinel node biopsy. A sentinel node biopsy is a procedure to determine whether cancer has spread to your lymph nodes. This procedure involves injecting a dye near the cancer. The dye then flows through the lymphatic system to your lymph nodes.

  The first lymph node that receives the dye is called the sentinel node. Your doctor removes this lymph node and looks for cancerous cells under a microscope.

• Imaging tests. Your doctor may recommend a chest X-ray and a CT scan of your chest and abdomen to help determine whether the cancer has spread to other organs.

  Your doctor may also consider other imaging tests such as a positron emission tomography (PET) scan or an octreotide scan - a test that uses an injection of a radioactive tracer to check for the spread of cancer cells.

Sentinel node biopsy. A sentinel node biopsy is a procedure to determine whether cancer has spread to your lymph nodes. This procedure involves injecting a dye near the cancer. The dye then flows through the lymphatic system to your lymph nodes.

The first lymph node that receives the dye is called the sentinel node. Your doctor removes this lymph node and looks for cancerous cells under a microscope.

Imaging tests. Your doctor may recommend a chest X-ray and a CT scan of your chest and abdomen to help determine whether the cancer has spread to other organs.

Your doctor may also consider other imaging tests such as a positron emission tomography (PET) scan or an octreotide scan - a test that uses an injection of a radioactive tracer to check for the spread of cancer cells.

Source: http://www.mayoclinic.com

Cancer that spreads to other parts of the body

Even with treatment, Merkel cell carcinoma commonly spreads (metastasizes) beyond the skin. Merkel cell carcinoma tends to travel first to nearby lymph nodes. Later it may spread to your brain, bones, liver or lungs, where it can interfere with the functioning of these organs. Cancer that has metastasized is more difficult to treat and can be fatal.

Source: http://www.mayoclinic.com

While exposure to sunlight isn't proved to cause Merkel cell carcinoma, it is considered a risk factor for this cancer. Reducing your sun exposure may reduce your risk of skin cancer. Try to:

• Avoid the sun during peak hours. Avoid sun exposure as much as possible during the strongest sunlight hours of the day — typically from 10 a.m. to 4 p.m. Move your outdoor activities to a time earlier in the morning or later in the day.
• Shield your skin and eyes. Wear a wide-brimmed hat, tightly woven clothing and sunglasses with ultraviolet light (UV) protection.
• Apply sunscreen liberally and often. Use a broad-spectrum sunscreen with an SPF of at least 15. Apply sunscreen generously, and reapply every two hours — or more often if you're swimming or perspiring.
• Watch for changes. If you notice a mole, freckle or bump that's changing in size, shape or color, talk to your doctor. Most skin nodules never become cancer, but catching cancer in its early stages increases the chances that treatment will be successful.

Source: http://www.mayoclinic.com

Factors that may increase your risk of Merkel cell carcinoma include:

• Excessive exposure to natural or artificial sunlight. Being exposed to ultraviolet light, such as the light that comes from the sun or from tanning beds, increases your risk of Merkel cell carcinoma. The majority of Merkel cell carcinomas appear on skin surfaces frequently exposed to sun.
• A weakened immune system. People with weakened immune systems — including those with HIV infection or those taking drugs that suppress the immune response — are more likely to develop Merkel cell carcinoma.
• History of other skin cancers. Merkel cell carcinoma is associated with the development of other skin cancers, such as basal cell or squamous cell carcinoma.
• Older age. Your risk of Merkel cell carcinoma increases as you age. This cancer is most common in people older than age 50, though it can occur at any age.
• Light skin color. Merkel cell carcinoma usually arises in people who have light-colored skin. Whites are much more likely to be affected by this skin cancer than are blacks.

Source: http://www.mayoclinic.com