Merkel cell carcinoma: Diagnosis, treatment and outcome

How is Merkel cell carcinoma diagnosed?

Diagnosis begins with an exam. Your dermatologist (or other doctor) will closely examine your skin and lymph nodes. We have lymph nodes in our neck, underarms, and other areas of the body. Lymph nodes help to protect us from illness. They often swell when we are sick.

If your doctor suspects Merkel cell carcinoma (MCC), you will need a skin biopsy. This is the only way to diagnose skin cancer. Your dermatologist can safely perform a skin biopsy during an office visit. To perform a skin biopsy, a dermatologist removes either the entire tumor or part of it.
What your dermatologist removes will be examined under a microscope. This magnified view allows a doctor to look for cancer cells.
Radiation treatments often play an important role in treating MCC.

How is Merkel cell carcinoma treated?

When the diagnosis is MCC, doctors with experience treating this rare skin cancer should be consulted. Each of these doctors should have expertise in a different field of medicine, such as dermatology, surgery, oncology, and radiation oncology. Working together, these doctors can create a treatment plan.

Before the doctors create a treatment plan, they want to find the stage of the cancer. Treatment differs for each stage. The stage tells doctors how deep the MCC has grown and whether the cancer has spread.

Finding the stage: To find the stage, a patient undergoes a process called staging. Staging for MCC often begins with an imaging test, such as a PET/CT scan. This allows the doctors to see if cancer has spread to organs inside the body.

After imaging tests, many patients diagnosed with MCC have a surgical procedure called a sentinel lymph node biopsy (SLNB). A SLNB can tell doctors if the cancer has spread to a patient’s lymph nodes. When MCC begins to spread, it often travels to a certain lymph node first. A SLNB can tell doctors to which lymph node the cancer would travel first and whether that lymph node or nearby lymph nodes contain cancer cells.

What happens during a SLNB

For many patients, a SLNB is an outpatient procedure. In some cases, getting a SLNB requires a short hospital stay. During this surgery, the following happens:
  1. The surgeon injects a dye, radioactive substance, or both into the patient. The injection is made near the MCC tumor.
  2. The surgeon uses a special device to follow the injected substance, which travels to the sentinel node (first node to which the cancer is likely to spread).
  3. The surgeon makes a small incision and removes the sentinel lymph node, and in some cases, other lymph nodes.
  4. A specially trained doctor, a pathologist, checks the removed lymph node(s) for cancer.
  5. If the pathologist finds cancer, the surgeon may remove more lymph nodes. Sometimes, the surgeon can do this during the same surgery. Sometimes, the patient needs a second surgery.

After finding and removing the lymph node(s), the surgeon may remove the Merkel cell tumor. Sometimes, removing the tumor requires another surgery.

Some patients need more imaging tests to help the doctors determine the stage of the cancer. A patient may need a CT scan, MRI, or CT/PET scan.

The stage of the cancer is determined by where it appears. The following summarizes the stages:
  • Local: Skin only.
  • Nodal: Skin and lymph nodes.
  • Metastatic: Cancer has spread beyond the skin and lymph nodes to other areas of the body.

Patients often have questions about what their stage means. You will find a table that shows the different stages for MCC at What are Merkel cell carcinoma "stages"?

The patient’s stage plays an important role in the treatment plan. The doctors also consider the patient’s age, overall health, and personal preferences. A treatment plan for MCC will consist of one or more of these treatments:
  • Surgery to remove the tumor.
  • Surgery to remove lymph nodes.
  • Radiation treatments.
  • Chemotherapy.
  • Clinical trial.

Excision (surgery): During this surgery, the surgeon removes the tumor and some surrounding tissue that looks healthy. Removing healthy looking tissue helps to catch cancer that may have traveled to an area that still looks healthy. An area can look healthy if it contains just a few cancer cells.

Mohs surgery: Because MCC often develops on the face and other areas with little fat, Mohs (pronounced "Moes") surgery may be recommended. This specialized surgery is used only to treat skin cancer. This surgery allows the Mohs surgeon to remove less healthy looking tissue.

During Mohs surgery, the Mohs surgeon cuts out the tumor plus a very small amount of healthy looking tissue surrounding the tumor. While the patient waits, the Mohs surgeon uses a microscope to look at what was removed. The surgeon is looking for cancer cells.

If the Mohs surgeon finds cancer cells in the healthy looking tissue, the surgeon will remove another small amount of healthy looking tissue and look at it under the microscope. This process continues until the surgeon no longer sees cancer cells.

MCC can grow deep, so some patients need reconstructive surgery. This surgery is usually performed immediately after the cancer surgery.

Lymphadenectomy: This is surgery to remove lymph nodes. This surgery is also called lymph node dissection.

Radiation treatments: This is often part of the treatment plan for MCC because this cancer has a high risk of returning after surgery. Studies show that radiation treatments reduce the risk of MCC returning. Patients usually begin radiation treatments within 4 weeks of having surgery to remove the cancer.

Radiation treatments also are given to patients who cannot undergo surgery. Findings from a study suggest that radiation alone can be an effective treatment.

Some patients receive radiation treatments to help them feel more comfortable. Your doctor may refer to this as palliative therapy. This therapy does not treat the disease. It helps people feel better.

Most patients receive radiation treatments in a hospital or outpatient facility. The treatments are usually given 5 days a week, Monday through Friday, for 5 weeks.


Chemotherapy
: Doctors recommend chemotherapy for some patients who have MCC that has spread beyond the skin and lymph nodes. Chemotherapy treats the cancer with drugs that can kill the cancer cells.

Clinical trial: Some patients are encouraged to join a clinical trial. A clinical trial is a type of research study. This study tests how well new a treatment or a new way of treating a disease works. For some patients joining a clinical trial may be the best treatment option.

What is the outcome for patients with MCC?

MCC is an aggressive cancer. It can return after treatment. It often returns within the first 6 to 12 months after diagnosis. For this reason, it is essential to keep all follow-up appointments with your doctors.

On a positive note, findings from a research study show that patients who do not have cancer in their lymph nodes have an excellent prognosis (outcome). Patients who have stage I, II, or III MCC tend to do better than patients who have MCC that has spread beyond the lymph nodes.

Every patient treated for MCC needs to keep all follow-up appointments. To learn what else you can do to manage MCC, be sure to read Merkel cell carcinoma: Tips for managing.

Learn more about Merkel cell carcinoma:

References:

Allen PJ, Bowne WB, Jaques DP, et al. “Merkel cell carcinoma: Prognosis and treatment of patients from a single institution.” J Clin Oncol. 2005; 23:2300-9

Bichakjian CK, Alam M, Andersen J et al. “Merkel cell carcinoma: Clinical practice guidelines in oncology.” National Comprehensive Cancer Network. Version 2.2013.

Colgan MB, Tarantola TI, Wearver AL et al. “The predictive value of imaging studies in evaluating regional lymph node involvement in Merkel cell carcinoma.” J Am Acad Dermatol. 2012; 67:1250-6.

Hawryluk EB, O'Regan KN, Sheehy N, et al. “Positron emission tomography/computed tomography imaging in Merkel cell carcinoma: a study of 270 scans in 97 patients at the Dana-Farber/Brigham and Women's Cancer Center.” J Am Acad Dermatol. 2013; 68:592-9.

Howle JR, Hughes TM, Gebski V et al. “Merkel cell carcinoma: an Australian perspective and the importance of addressing the regional lymph nodes in clinically node-negative patients.” J Am Acad Dermatol. 2012; 67:33-40.

Pape E, Rezvov N, Penel N, et al. “Radiotherapy alone for Merkel cell carcinoma: a comparative and retrospective study of 25 patients.” J Am Acad Dermatol 2011; 65:983-90.

Tarantola TI, Vallow LA, Halyard MY, et al. “Prognostic factors in Merkel cell carcinoma: Analysis of 240 cases.” J Am Acad Dermatol. 2013; 68:425-32.

Tarantola TI, Vallow LA, Halyard MY, et al. “Unknown primary Merkel cell carcinoma: 23 new cases and a review.” J Am Acad Dermatol. 2013 68:433-40