Merkel cell carcinoma

What is Merkel cell carcinoma?

Merkel cell carcinoma (MCC) also known as Merkeloma, cutaneous neuroendocrine carcinoma, or trabecular carcinoma is a rare type of skin cancer that usually appears in the head and neck region (50.8%) or the extremities (33.7%). It appears as a bluish red or flesh-colored nodule most often on the face, head, or neck.

Metastasis of Merkel cell cancer

Where does Merkel cell cancer spread to? Merkel cell carcinoma tends to grow quickly and metastasize at an early stage. Merkel cell carcinoma can spread to regional lymph nodes and then may spread to distant parts of the body, such as the lungs, brain, bones, or other vital organs.

Survival rates for Merkel cell carcinoma

Merkel cell carcinoma is a rare but aggressive type of skin cancer with a low survival rate with no specialized treatment. The five-year relative survival rate for a specific stage of Merkel cell carcinoma is 70%, which means that people who have Merkel cell cancer can live for at least 5 years after their diagnosis.

A person’s response to treatment may affect the chance of survival. The 5-year survival rate for stage 4 melanoma is 15–20 percent.

Causes of Merkel cell carcinoma

The exact cause of Merkel cell carcinoma is not known. However, research shows that the virus Merkel cell polyomavirus plays a role in causing most cases of Merkel cell carcinoma. The virus lives on the skin without showing any signs or symptoms. Other risk factors may also play a vital role in the development of Merkel cell cancer.

Signs and Symptoms of Merkel cell carcinoma

The first sign of Merkel cell carcinoma is usually single pink, red, or purple shiny bump. The bump may be skin-colored and does not hurt. Most Merkel cell carcinomas appear as a fast-growing, painless tumors on your exposed skin or on areas that are not directly exposed to sunlight. If you notice a mole, bump, or freckle that changes in size, shape, or color, then you must see your dermatologist.

Factors affecting the prognosis of Merkel cell carcinoma

Merkel cell carcinoma is highly curable if it is diagnosed in an early stage. If tumors have no involvement of lymph nodes then patients have a greater than a 60% chance of long-term survival.

Treatments may be surgical and non-surgical, radiation, and chemotherapy, depending upon the following factors:

  1. The size of the tumor,
  2. Degree of spread,
  3. The general health of the patient,
  4. The location of the tumor,
  5. And the depth of Merkel cell carcinoma tumor.

General risk factors of Merkel cell carcinoma

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

  1. Merkel cell carcinoma usually arises in people who have light-colored skin such as White people are more likely to get skin cancer than black people.
  2. People who have a weak immune system or those who have HIV infection or chronic leukemia are more likely to develop this cancer.
  3. Merkel cell carcinoma risk increases with age. This cancer is most common in people older than age 50.
  4. Merkel cell carcinoma is also associated with the development of other skin cancers, such as squamous cell or basal cell carcinoma.
  5. Long-term exposure to ultraviolet light and sunlight increases the risk of Merkel cell carcinoma.
  6. People who are exposed to artificial sunlight such as from tanning beds, psoralen, and ultraviolet A (PUVA) therapy for psoriasis.
Merkel cell carcinoma on the right eyebrow
Patient with Merkel cell carcinoma of the right eyebrow

Note: This work, “Patient with Merkel cell carcinoma of the right eyebrow”, is a derivative of “Patient with Merkel cell carcinoma of the right eyebrow” originally published in an article on by Sven Schneider et al, used under CC BY. This updated version of the work is licensed under CC BY by King.

Stages of Merkel cell carcinoma

Tumor sizes are measured in centimeters or inches. Common food items that are usually used to show tumor size in cm include:

a pea (1 cm), a peanut (2 cm), a grape (3 cm), a walnut (4 cm), a lime (5 cm or 2 inches), an egg (6 cm), a peach (7 cm), and a grapefruit (10 cm or 4 inches).

There are five main stages in Merkel cell Carcinoma:

  1. Stage 0
  2. Stage I
  3. Stage II
  4. Stage III
  5. Stage IV

Stage 0 Merkel cell cancer

(carcinoma in situ) The cancer is only in the epidermis and hasn’t spread to the lymph nodes.

Stage 1 Merkel cell cancer

The cancer is less than 2 cm across and hasn’t grown into the lymph nodes.

Stage 2 Merkel cell cancer

  • In stage IIA,  the tumor is more than 2 cm
  • In stage IIB, the tumor has spread to nearby connective tissues, muscle, cartilage, or bone.

Stage 3 Merkel cell cancer

It is divided into stages IIIA and IIIB.

In stage IIIA, either of the following is found:

  1. The tumor may be any size and has spread to nearby connective tissues, muscle, cartilage, or bone. A lymph node can’t be felt during a physical exam but cancer is found in the lymph node.
  2. Or, a swollen lymph node is felt during a physical exam and/or seen on an imaging test.

In stage IIIB, the tumor may be any size and:

  • May have spread to nearby connective tissue, muscle, cartilage, or bone. A swollen lymph node is felt during a physical exam and/or seen on an imaging test.
  • cancer is in a lymph vessel between the primary tumor and lymph nodes that are near or far away.
  • Cancer may have spread to lymph nodes.

Stage 4 Merkel cell cancer

In this stage, the tumor has spread to skin that is not close to the primary tumor or the distant parts of the human body such as bone, liver, lungs, and brain.

Diagnosis of Merkel cell carcinoma

Tests and procedures used to diagnose Merkel cell carcinoma include:

  1. Physical exam: Your dermatologist will examine your skin for unusual moles, freckles, spots, and other lumps.
  2. Removing a sample of suspicious skin: Your doctor will remove the tumor or a sample in a procedure called a skin biopsy. The sample will be sent to a laboratory for the analysis of cancer cells.
  3. Positron emission tomography: PET scan or an octreotide scan, a test that uses an injection of a radioactive tracer to detect the spreading of cancer cells.
  4. Sentinel node biopsy: A sentinel node biopsy procedure involves injecting a dye near cancer. This dye then flows through the lymphatic system. Your doctor removes sentinel nodes and looks for cancerous cells under a microscope.
  5. Full-body skin exam:  A doctor checks for abnormal growths on the entire body.
  6. Imaging tests: Your doctor may recommend a CT scan, or chest X-ray to determine whether cancer has spread to other organs.

Treatment options to deal with Merkel cell cancer

There are different types of treatment for patients with Merkel cell carcinoma. Four types of standard treatment are used:

  1. Chemotherapy
  2. Immunotherapy
  3. Radiation therapy
  4. Surgery

How to prevent yourself from Merkel cell carcinoma

  1. Avoid direct sunlight exposure.
  2. Avoid the sun during peak hours when sunlight is very strong.
  3. Apply sunscreen on your body.
  4. If you notice a mole, freckle, or bump that is changing in size, shape, or color, see your dermatologist.
  5. Wear a wide-brimmed hat, tightly woven clothing, and sunglasses to protect yourself from ultraviolet light.

Who is most susceptible to Merkel cell carcinoma

Merkel cell carcinoma most often develops in older people with an equal incidence in men and women. About 78% of patients are older than 60 years. Long-term sun exposure or a weak immune system may increase the risk of developing Merkel cell carcinoma.

MCC occurs mostly in white elderly people. Black people have less risk of getting el cell carcinoma. It may be slightly more common in females. After 60 years, MCC is more often seen in female patients.

MCC occurs more frequently in immunosuppressed patients, transplant recipients, and HIV-infected patients.

Merkel Cell Carcinoma FAQs

What is a Merkel cell and what is its importance?

Merkel cells are also known as Merkel-Ranvier cells or tactile epithelial cells. Merkel cells are oval-shaped mechanoreceptor cells that are found right below the epidermis. These cells are very close to the nerve endings and are essential for the sensation of touch.

What are Merkel receptors?

Merkel nerve endings are a type of sensory receptor, that are found in the basal epidermis and hair follicles. Each end consists of a Merkel cell in close apposition with an enlarged nerve terminal. This is sometimes referred to as a Merkel disc receptor.

What is the rarest skin cancer?

Merkel cell skin cancer is a rare and deadly skin cancer that has a high risk of recurring and spreading throughout the patient’s body. Its recurrence takes place within two years after diagnosis of the primary tumor.

How likely is it to get Merkel cell carcinoma from tanning beds?

Using indoor tanning beds before age 35 can increase your risk of melanoma and other skin cancer, by 59 percent. Tanning beds increase your risk of MCC, especially in women younger than 30 who are 6 times more likely to develop skin cancer if they tan indoors.

Is Merkel cell carcinoma fatal?

Merkel cell cancer is a rare, highly malignant primary cutaneous carcinoma that tends to travel first to nearby lymph nodes. Later it may spread to your brain, bones, liver, or lungs. Merkel cell cancer that has metastasized is more difficult to treat and can be fatal.

What does Merkel cell cancer look like?

Merkel cell carcinomas are blue, red, or flesh-colored lumps that appear on sun-exposed areas of the skin. The prognosis for MCC that has spread is poor.

Does Merkel cell carcinoma itch?

Merkel cell skin cancer starts on areas of the body that are exposed to the sun, especially the face, neck, arms, and legs, but it can occur anywhere on the body. It often appears as a single pink, red, or purple shiny bump that usually doesn’t hurt or itch.

Does Merkel cell cancer run in families?

Merkel cell carcinoma (MCC) does not seem to run in families. While DNA mutations are found in the cells of MCC tumors that can lead to MCC, however, these mutations are somatic type mutations that occur only during a person’s lifetime and they have nothing to do with the inheritance. So Merkel cell cancers do not run in families.

Is Merkel cell carcinoma malignant?

Merkel cell cancer is a rare form of cancer in which malignant cells form in the skin. A weak immune system and Sun exposure may affect the risk of Merkel cells.

Is Merkel cell skin cancer painful?

MCC usually appears as a single pink, red, or purple shiny bump that usually doesn’t hurt.

What is metastatic Merkel cell carcinoma?

Merkel cells are found in the epidermis of the skin.  MCCs tend to metastasize quickly 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.

How do you get Merkel cell polyomavirus?

Merkel cell carcinomas are associated with the mutations caused by exposure to ultraviolet (UV) light and ionizing radiation.

Is Merkel cell carcinoma the same as melanoma?

Melanoma and Merkel cell carcinoma (MCC) are both aggressive skin malignancies associated with ionizing radiation, immunosuppression, and exposure to Ultraviolet rays. Unlike melanoma, Merkel cell carcinoma is rare.

What is meant by Recurrent Merkel cell carcinoma?

Recurrent Merkel cell carcinoma is cancer that has recurred or come back after it was treated. It is common for Merkel cell carcinoma to come again/recur.

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