What is Merkel Cell Carcinoma of the Skin?
Merkel cell carcinoma (MCC) is a rare and aggressive type of skin cancer, which is becoming increasingly common. It usually appears in the head and neck area of elderly white men. Risk factors for MCC include exposure to ultraviolet (UV) rays, getting older, and having a weakened immune system. Also, having an infection from the Merkel cell polyomavirus (MCPyV) can contribute to the development of this cancer.
To diagnose this condition, a skin biopsy—a test where a small sample of skin is removed and checked under a microscope—needs to be done. It’s also important to check the closest lymph nodes (small organs that produce and store cells that fight infection and disease), given that MCC tends to progress quickly. This can be done through a process called a sentinel lymph node evaluation.
The main treatment for MCC is surgical removal of the tumor, which may also be followed by radiotherapy—a treatment that uses high-energy rays to destroy cancer cells. Treatments for MCC that has spread to other parts of the body are being developed and some of them, which are aimed at boosting the immune response against cancer, have shown promising results.
What Causes Merkel Cell Carcinoma of the Skin?
The exact cell that becomes the starting point for MCC, a skin cancer, is still debated. Some believe it could be one of the basic skin cells. Studies have found a virus called MCPyV in most (80%) cases of MCC, suggesting that this virus could play a role in causing this type of cancer.
MCPyV is a very small, uncoated virus composed of two strands of DNA, and belongs to a family of viruses known as polyomaviruses. Many people are infected with MCPyV, but don’t show any symptoms. However, in cases of MCC, the virus’ DNA integrates into the host’s genetic material.
We do know some risk factors for developing MCC. These include exposure to sunlight (UV rays), getting older, and a weakened immune system.
Risk Factors and Frequency for Merkel Cell Carcinoma of the Skin
Over the past several years, the number of new cases being diagnosed each year for a certain condition has been rising steadily, now reaching about 2,000 new cases annually. This is probably due to improved methods of diagnosis and an increase in the known risk factors. This condition tends to affect older males most often, with over 90% of patients being Caucasian. It usually shows up in areas of the body that get the most sun, particularly around the head and neck.
Signs and Symptoms of Merkel Cell Carcinoma of the Skin
Merkel cell carcinoma (MCC) usually shows up as a quick-growing, firm, red-purple lump on skin that often gets sun exposure. It’s most frequently found on the head and neck. Sometimes, it might show up as a lump beneath the skin, without causing any changes to the skin’s surface. Conditions that might look similar to MCC include a basal cell carcinoma, a type of melanoma that doesn’t produce pigment, squamous cell carcinoma, an epidermal inclusion cyst, or a type of growth called a pyogenic granuloma.
This cancer usually starts in the skin, but it can also begin in other parts of the body, like the saliva glands or the nasal cavity. MCC tends to be aggressive, and as a result, at the time of diagnosis, only 65% of patients have cancer that hasn’t spread beyond its original location. It has also been found to occur concurrently with other types of skin cancer, such as squamous cell carcinoma, basal cell carcinoma, or a type of cancer called sebaceous carcinoma.
Testing for Merkel Cell Carcinoma of the Skin
Confirming a diagnosis for MCC, also known as Merkel cell carcinoma, requires a skin test known as a biopsy. This is where a small sample of skin is taken and examined under a microscope. Besides doing a biopsy, checking the lymph nodes is also necessary for everyone, regardless of the stage of the disease.
If you have a lymph node that appears to be affected, you’ll need a procedure called fine needle aspiration or a core biopsy for further examination. If your lymph nodes look normal, a special type of biopsy known as sentinel lymph node biopsy will be done, to make sure.
For those patients whose disease has spread to the lymph nodes, more detailed tests are necessary. This includes imaging tests to get a clear picture of the inside of your body. A type of scan known as a PET/CT is typically the best choice for these situations.
Treatment Options for Merkel Cell Carcinoma of the Skin
Before deciding on the best treatment method, doctors always investigate to see whether cancer cells have spread to the lymph nodes, which are parts of the immune system located throughout the body.
If the cancer is limited to the initial site (local disease), the National Comprehensive Cancer Network (NCCN) recommends that doctors remove the primary tumor with a fairly wide margin. This could involve Mohs micrographic surgery, a precise surgical technique used to treat skin cancer. Radiation therapy can then also be used in some specific cases to make sure no cancer is left behind.
If the cancer has spread to the nearby lymph nodes (locoregional disease), doctors will usually remove these affected nodes and/or use radiation targeting the area containing these lymph nodes. Decisions to use radiation therapy will depend on the extent of the disease among other factors.
If the disease has spread further to other parts of the body (metastatic disease), a team of experts will discuss the best approach, which might involve a clinical trial if available or the use of other treatments like systemic therapy, radiation therapy, and/or surgery. Systemic agents are medications that can circulate the body and target cancer cells and can include chemotherapy and immunotherapy. Immunotherapy uses your body’s immune system to fight the cancer and can have promising results; pembrolizumab, nivolumab, and avelumab are examples of such treatments.
Once the patient is diagnosed with Merkel cell carcinoma (MCC), a type of aggressive skin cancer, they should be followed every three to six months for three years and afterward every six to 12 months, for routine complete skin and lymph node exams. Imaging studies may also be needed, especially in high-risk patients or as indicated by the patient’s condition.
What else can Merkel Cell Carcinoma of the Skin be?
When discussing skin issues, there are several conditions that might come into consideration. These include:
- Basal cell carcinoma (a type of skin cancer that grows in the basal cells of your skin)
- Cutaneous melanoma (a skin cancer that begins in cells called melanocytes)
- Cutaneous squamous cell carcinoma (another type of skin cancer that forms in squamous cells)
- Dermatofibroma (a common, non-cancerous, small bump in the skin)
- Keratoacanthoma (a growth that develops on the skin).
- The skin changes (dermatologic manifestation) of metastatic carcinomas (cancers that have spread from their original site to other parts of the body)
What to expect with Merkel Cell Carcinoma of the Skin
Merkel cell carcinoma (MCC) is a rare and serious type of skin cancer that often has spread to nearby or distant body parts at the time it’s diagnosed. The patient’s outlook depends on how advanced the cancer is when it’s first found. Statistics suggest that after five years, 51% of patients with localized cancer are still alive, falling to 35% for patients with cancer that has spread to nearby lymph nodes, and 14% for patients where the disease has spread more widely.
One of the best predictors of long-term survival without the disease coming back is whether a biopsy of the “sentinel” lymph nodes (the first lymph nodes the cancer is likely to spread to) does not find any cancer cells. This is particularly true for patients diagnosed at an early stage.
Patients whose tumors are less than 2 cm when first found also have a higher chance of surviving for ten years. Other factors associated with a better outcome include being female, having a small tumor (less than 2 cm), and having the cancer located on the upper limbs.
