What Is Merkel Cell Carcinoma?
Merkel cell carcinoma (MCC), otherwise called neuroendocrine carcinoma of the skin, is a skin cancer that usually results in skin-colored or bluish-red nodules on the face, neck, or head. It is a type of cancer that originates from the cells in the skin called Merkel cells. These cells grow uncontrollably to form lesions. This cancer is often seen in older adults (above the age of 70 years), and long-term sun exposure or a weakened immune system increases the risk. This skin carcinoma grows fast and spreads quickly to other parts of the body. The treatment options for MCC depend on whether the cancer cells have spread beyond the skin.
The cells seen in this cancer resemble Merkel cells, which are located close to the skin’s nerve endings. These cells share traits with nerve and endocrine or hormone-producing cells, because of which they are called neuroendocrine cells, and MCC is sometimes referred to as neuroendocrine carcinoma of the skin. Trabecular carcinoma is another name for MCC. It is a rare tumor, and in the year 2018, around 2000 people were diagnosed with MCC in the United States (US). But between the years 2000 and 2013, the US saw a 95 % increase in the number of people diagnosed with this carcinoma, which is due to the increasing population of older adults.
What Are the Symptoms of Merkel Cell Carcinoma?
A reddish-purple, painless, fast-growing, and hard lump or nodule is the main symptom of Merkel cell carcinoma. This lump can form anywhere on the body, but it most commonly develops in the areas exposed to sunlight, such as the legs, face, arms, head, and neck. When cancerous cells spread to the lymph nodes, the nodes can become enlarged and form a lump under the skin.
Merkel cell carcinoma is hard to diagnose without a biopsy, as it looks like many other types of skin cancer. In case you develop an abnormal growth anywhere on your skin or have irregularly shaped moles, or develop rough, red, pink, or brown patches on the skin, consult your doctor immediately. It need not necessarily be a sign of cancer, but a complete examination by a dermatologist is necessary.
Some of the differentiating characteristics of MCC are:
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Firm and raised bump.
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Red, purple, or pink in color.
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Usually painless, but can bleed or form sores and become painful.
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Rapid growth.
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It can resemble an insect bite or stye.
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It can form new and smaller lumps under the skin.
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It can result in lymph node enlargement.
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It measures 1.7 cm in diameter and is dome-shaped.
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It is not darkly pigmented as malignant melanoma or scaly like squamous cell carcinoma.
What Causes Merkel Cell Carcinoma?
Doctors are still not sure what causes Merkel cell carcinoma. This carcinoma begins in the Merkel cells, the cells found in the epidermis (the outermost layer of the skin). As Merkel cells are close to the nerve endings of the skin, they are responsible for the sense of touch. Recently, a common virus was found to play a role in causing Merkel cell carcinoma. This virus, Merkel cell polyomavirus, lives on the human skin and does not result in any signs or symptoms, and how it causes this carcinoma is not yet determined. As this is a common virus and MCC is so rare, it is most likely that other risk factors play a role in forming MCC.
Risk Factors:
The following factors may increase the risk of a person developing Merkel cell carcinoma:
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Excessive Sunlight Exposure - No matter the source of UV (ultraviolet) light, both natural sunlight and artificial light (light from tanning beds) increase the risk of Merkel cell carcinoma. The commonly affected areas are the skin surfaces that are frequently exposed to the sun.
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Advanced Age - The majority of patients diagnosed with MCC are above the age of 50 years.
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Lighter Skin Tone - Those with a fair skin tone more commonly develop Merkel cell carcinoma than those with a darker skin tone.
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Weak Immunity - People with a weakened immune system, such as those infected with HIV (human immunodeficiency virus), cancer patients, and those taking immunosuppressants, are at more risk of MCC.
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A History of Other Skin Cancers - People with a history of basal cell carcinoma, squamous cell carcinoma, or other skin cancers are more at risk of developing Merkel cell carcinoma.
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Sex - Men are twice as likely to develop MCC than women.
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Infection With Merkel Cell Polyomavirus - Almost eight out of ten patients diagnosed with MCC have this virus present in the cancerous cells.
How Is Merkel Cell Carcinoma Diagnosed?
If your doctor sees any abnormal moles, pigmentation, freckles, or other growths on your skin, he or she will do a biopsy. During the biopsy, a sample of this suspicious lesion is taken, which is sent to the laboratory to look for signs of cancerous cells.
Once the biopsy results show abnormal or cancerous cells, the doctor will conduct additional tests to determine the extent and how far cancer has spread. The tests that might be required are:
1) Sentinel Node Biopsy - This test is done to determine if the cancerous cells have spread to the nearby lymph nodes. Here, a dye is injected near cancer. This dye reaches the lymph nodes through the lymphatic system. The lymph nodes that receive the dye first are called sentinel nodes. These sentinel nodes are removed and examined for cancerous cells.
2) Imaging Tests - Tests like X-ray, CT (computed tomography), MRI (magnetic resonance imaging), positron emission tomography (PET) scan, octreotide scan, etc., are also used to check if cancer cells have spread to other parts of the body.
Merkel Cell Carcinoma Staging:
Based on the results of the above diagnostic tests, the stages of Merkel cell carcinoma are:
Stage 0 - Cancer cells are only present in the upper layer of the skin (epidermis) and have not spread to the nearby lymph nodes.
Stage 1 - Cancer is less than 2 cm in diameter and has not affected the nearby lymph nodes.
Stage 2 - Cancer is greater than 2 cm in diameter and has not spread to the nearby lymph nodes.
Stage 3 - Cancer has spread to the nearby lymph nodes and tissues.
Stage 4 - Apart from cancer spreading to the nearby lymph nodes and tissues, it has also spread to distant areas like the lungs, brain, and bones.
How Is Merkel Cell Carcinoma Treated?
The following are the treatment options for Merkel cell carcinoma:
1) Surgery:
The surgeon removes the tumor along with the borders of the surrounding normal skin. The lymph nodes are also surgically removed if there is evidence of a spread.
2) Radiotherapy:
Radiotherapy is the use of high-energy beams (X-rays or protons) to destroy cancer cells.
3) Immunotherapy:
Here, medicines that help the immune system fight cancer cells are administered.
4) Chemotherapy:
Medicines are either administered orally or intravenously to kill cancer cells.
Can Merkel Cell Carcinoma Be Prevented?
Even though the exact cause of MCC is not known, the risk of this cancer can be reduced significantly by avoiding exposure to sunlight. You can:
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Avoid going out during the strongest sunlight hours every day (from 10 AM to 4 PM).
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Wear a hat, sunglasses (with ultraviolet protection), and tightly woven clothes to protect from harmful sun rays.
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Apply sunscreen (sun protection factor should be a minimum of 30), even if it is cloudy outside.
Conclusion:
With the help of the preventive measures mentioned above, it is possible to reduce the chances of MCC to some extent. The evidence and efficacy of treating this condition with immunotherapy and targeted molecular therapy are still under study. If any unusual changes are noticed on the skin, it is always better to seek medical help as soon as possible.