Merkel cell carcinoma occurs when cells in the outer layer of your skin grow out of control. It usually develops in sun-exposed areas and grows quickly over weeks to months.
It can spread (metastasize) through the lymph system or blood to other parts of your body. It can also recur after treatment.
Risk factors
Merkel cells are small, oval-shaped skin cells that help with the sense of touch. Rarely, these cells can begin growing uncontrollably and form a tumor. They most often appear on areas of the body that receive greater sun exposure. They may be a shiny, painless bump or lump that is a flesh-toned, red, purple or bluish color and is usually smaller than a quarter. They may look like an insect bite or a pimple, and they can grow rapidly over weeks to months.
Many factors can increase your risk of developing MCC, including having a weakened immune system. This is a common problem for people who have chronic lymphocytic leukemia or who are recipients of organ transplants or are taking drugs that suppress the immune system. People with light skin are at higher risk than those with darker skin because their skin offers less protection against UV rays. Also, aging increases your risk of developing Merkel cell carcinoma.
Scientists recently discovered that a common virus called the Merkel cell polyomavirus is found in about 80% of MCC cases. However, researchers do not know what causes the virus to turn into cancer in some people and not in others.
Everyone should do regular self-exams to check for any new or changing marks on the skin, especially those that itch, bleed, crust, or change in shape. If you notice any of these signs, see your doctor right away.
Symptoms
Merkel cell carcinoma starts on sun-exposed areas of the skin — usually the face, neck and arms — but can appear anywhere on the body, even in areas typically protected from the sun. The first symptom is usually a painless lump or bump that grows rapidly, often within weeks. The lump may be the size of a pea or smaller, and it can appear to be red, scaly or purple. It can grow into a wound or break open, and it may bleed easily. The cancer can also spread to nearby lymph nodes or to other parts of the body, such as the liver, bone and lungs.
Researchers don’t know what causes Merkel cell carcinoma. They do know that it has something to do with the Merkel cells, and they think that a common virus called the Merkel cell polyomavirus might trigger this rare cancer in these cells. But they need more research to confirm this link.
People with a weak immune system are more likely to develop Merkel cell carcinoma. This includes people who are HIV-positive, have had an organ transplant or take immunosuppressive drugs. It’s also more common in men than in women. And it appears more frequently in people with lighter skin.
Merkel cell carcinoma is rarely fatal, but it can be difficult to treat because the cells spread so quickly. That’s why early detection and treatment are so important.
If you notice a growth or bump that’s changing in shape, size or color, or if it hurts when touched, talk to your doctor right away. Your doctor will examine your bump or lesion and do a biopsy to check for Merkel cell carcinoma. If the tumor is small and not spreading, your doctor might recommend surgery to remove it. A wide excision might be needed, and the surrounding lymph nodes may be removed or treated with radiation after surgery.
If the cancer has spread, your doctor will order other tests to find out where it is in the lymph nodes and in the rest of the body. These tests might include a CT scan or an MRI of the head, chest and abdomen. They might also order a positron emission tomography (PET) scan or a sentinel node biopsy, in which they take a sample of lymph nodes near the skin bump and check for signs of cancer.
Diagnosis
Merkel cell carcinoma is a rare and often aggressive skin cancer. It develops in Merkel cells found in the skin’s outer layer and spreads quickly to other parts of the body. It also tends to recur and comes back after treatment. It’s important for physicians to be aware of this cancer and recognize it when it appears.
A physician can often diagnose merkel cell carcinoma by taking a small sample of the growth for examination under a microscope (biopsy). The person should inform their doctor of any unusual symptoms that may be present. The doctor will take a detailed medical history, including any past surgeries or treatments.
Physicians will also perform a physical exam to assess the growth’s characteristics. They will note the size, texture and color of the growth and ask about any other unusual symptoms. They will then order an imaging test, such as an X-ray or CT scan, to check if the tumor has spread.
If the growth is not a melanoma, but it is a malignant tumor, the doctor will usually refer the person to a specialist in skin cancer (dermatologist). The dermatologist will perform a biopsy of the growth and send it to a lab for testing. They will look for characteristic Merkel cell carcinoma pathology and, if possible, a clonal immunoglobulin chain rearrangement on cytokeratin-20 (CK20) to confirm the diagnosis.
A lymph node biopsy might be performed to check for the presence of Merkel cell carcinoma in nearby lymph nodes. It is common for these cancers to spread to the lymph nodes in the early stages of the disease.
Chemotherapy is sometimes used to treat merkel cell carcinoma. The most commonly used chemotherapy drugs for this type of cancer are cisplatin (Platinol AQ, Paraplatin, Carboplatin) and etoposide (Vepesid, VP-16, Hycamtin). These drugs can be given through a needle into a vein (intravenously), or they can be taken as pills. They are given for a short time period, usually every few weeks.
Surgical excision of the primary tumor is the main treatment for merkel cell carcinoma. In addition, the patient may be treated with radiotherapy postoperatively, especially in cases of large lesions or where immunosuppression is a risk factor.
Treatment
Merkel cells are located deep in the epidermis (top layer of skin) and sit near nerve endings that provide our sense of touch. Merkel cell carcinoma occurs when these cells grow out of control and form tumors, which can affect nearby skin or spread to other tissues and lymph nodes.
This rare cancer is found mostly on the head, neck and arms but may also appear on the torso, legs and eyelids. It most often appears as a firm, raised lump or bump, typically red or purple and not painful. In some cases, the cancer may break open into a wound or sore. Merkel cell carcinoma is very fast-growing and can spread to other parts of the body, particularly the lungs and brain. If the cancer spreads, it is considered metastatic and more difficult to treat.
After a Merkel cell carcinoma is diagnosed, doctors will use tests to find out how far the cancer has spread. This process is called staging. The stage of the disease helps determine which treatment options are best.
The most common treatment option for Merkel cell carcinoma is surgery to remove the tumor. Depending on the stage, your doctor will either remove a wide area around the tumor or perform Mohs surgery to remove the tumor in layers and leave as much healthy tissue as possible. Generally, we will also treat the primary site with radiation after surgery to increase the chance of a complete cure.
Our expert team has extensive experience treating Merkel cell carcinoma. We offer the latest in specialized treatments, including immunotherapies that boost your body’s natural defenses to fight the cancer. Our coordinated care team will work with you to develop an individualized treatment plan.
After your treatment, we will follow up with regular clinic visits and radiologic testing. This includes a positron emission tomography (PET) scan or CT scan and an MRI of the brain. This will help us keep an eye out for any recurrence of the Merkel cell carcinoma and look for signs that the cancer has spread. People who have had one Merkel cell carcinoma are at higher risk for having more skin cancers in the future.
