Because Merkel cell carcinoma is rare, the diagnosis usually comes as a surprise to both the doctor and the patient. Patients visit their doctor because of a change in their skin or a spot that is getting larger.
Diagnosis
Merkel cell carcinoma is diagnosed by means of a skin biopsy (tissue sample), which is then examined under a microscope by a pathologist. Common types of biopsies include the punch biopsy (in which a small sample is removed) and the shave biopsy (in which a portion of the surface of the abnormal area (lesion) is removed with a scalpel). The pathologist then performs immunohistochemical staining on the biopsy to determine whether a lesion is Merkel cell carcinoma or, for example, a melanoma (malignant melanoma).
How is it determined whether a Merkel cell carcinoma has already metastasized?
Merkel cell carcinoma cells can migrate from the skin to the lymph nodes via lymphatic vessels. If a lymph node feels enlarged, it may contain macrometastases. Sometimes lymph nodes may contain metastases but not be enlarged (micrometastases). The sentinel lymph node is the first lymph node in the drainage area of a malignant tumor. Sentinel lymph nodes should therefore be removed surgically (lymphadenectomy) to determine whether metastases are present.
Is it difficult for a pathologist to diagnose Merkel cell carcinoma?
No, although Merkel cell carcinoma usually looks quite inconspicuous on the skin (e.g., like a cyst), it can be easily identified as Merkel cell carcinoma under a microscope. In most cases, the pattern revealed by specific staining techniques and other tests makes it very easy for the pathologist to diagnose Merkel cell carcinoma.
Do I need imaging tests?
CT, X-ray, MRI, bone scan, and PET scans are different types of imaging used to look inside the body. They are used to detect cancerous lesions inside the body. They are particularly important when Merkel cell carcinoma has spread to the lymph nodes, in order to determine whether metastases have also developed elsewhere
Treatment
There are several types of treatment for Merkel cell carcinoma, which are used in different situations—including in combination or one after another. There are three main treatments for Merkel cell carcinoma:
- surgical excision (removal) of the primary lesion and/or lymph nodes,
- Radiation therapy and
- Systemic therapy, including chemotherapy and immunotherapy.
The goal of surgical excision is to remove the Merkel cell carcinoma (primary tumor) in such a way that it does not recur in the immediate vicinity or in the nearby lymph nodes. Therefore, the tumor should be excised over a large area, leaving an appropriate safety margin. Unfortunately, however, even when the tumor is removed with > 2-centimeter margins, Merkel cell carcinoma may recur. The risk of local recurrence—which varies depending on the stage of cancer—can be significantly reduced through the concurrent (adjuvant) use of radiation therapy. Radiation therapy (radiotherapy) is the treatment of cancer with ionizing radiation.
Radiation therapy damages the genetic material of cancer cells and prevents their growth. However, radiation therapy also damages healthy cells in the area exposed to radiation. Radiation therapy is administered to patients who are at risk of tumor spread and who want to reduce the likelihood of recurrence.
Unlike radiation therapy (local treatment), chemotherapy fights cancer throughout the entire body (systemic treatment). Chemotherapy aims to target cancer cells that are dividing uncontrollably and growing rapidly. However, this process also affects healthy, rapidly dividing cells. Patients with metastatic Merkel cell carcinoma may be treated with chemotherapy, especially if the tumor has spread to distant organs such as the lungs or liver. However, the success of various chemotherapy treatments for advanced Merkel cell carcinoma has been rather limited to date and has been associated with some serious side effects.
Immunotherapy is a method of treating cancer that involves using substances to restore the body’s immune cells’ ability to recognize and destroy tumor cells.
There are several therapies that can stimulate the immune system. These include, for example, vaccines, genetically modified immune cells, and checkpoint inhibitors (anti-PD-1 or anti-PD-L1 antibodies). Tumor cells evade the immune system by activating molecular “brakes” (such as the PD-1 protein) on the surface of the body’s own immune cells. Checkpoint inhibitors cause these brakes to be released, allowing the immune cells to function again and fight the tumor.
For patients with advanced Merkel cell carcinoma—such as those with distant metastases or Merkel cell carcinoma that cannot be surgically removed—these medications may be an option. Side effects of immunotherapy can affect any organ. If you experience any side effects, you must contact your treating physician. The most common side effects are: fatigue, gastrointestinal symptoms, rash, and cough.
Follow-up Care
Optimal medical care for the treatment of Merkel cell carcinoma can be ensured by a team consisting of dermatologists, surgeons, oncologists, and radiation oncologists. After your first treatment, you must have regular skin and lymph node checkups. Visits should take place approximately every one to three months during the first year, every three months during the second year, every six months from the third to the fifth year, and annually thereafter.
Merkel Cell Carcinoma Follow-up Care Protocol: Version for Physicians
Follow-up Care for Merkel Cell Carcinoma
Is Merkel cell carcinoma hereditary, and could my children develop it?
There is no data to suggest that there is a genetic or familial predisposition to Merkel cell carcinoma.
What precautions should you take to prevent skin cancer?
Since UV radiation is believed to be the primary cause of Merkel cell carcinoma, excessive UV exposure should be avoided. This is especially true if you have previously been diagnosed with Merkel cell carcinoma.
