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Merkel Cell Carcinoma (MCC)

Harold C. Simmons Comprehensive Cancer Center

UT Southwestern Medical Center's experienced skin cancer specialists deliver expert care to people with all stages of Merkel cell carcinoma (MCC). Our patients have access to the most innovative therapies and clinical trials that aren't available at every hospital.

UT Southwestern is home to the only National Cancer Institute-designated comprehensive cancer center in North Texas. Patients with Merkel cell carcinoma receive a unique level of expertise and experience, as well as the most advanced and innovative therapies available. 

Expert Care for a Rare Skin Cancer

Merkel cell carcinoma (MCC) is a very rare form of skin cancer that can develop when the Merkel cells – a type of neuroendocrine cell in the skin – grow uncontrollably.

Approximately 2,000 cases of Merkel cell carcinoma are diagnosed annually, with the number of cases increasing every year.

Because this type of cancer can grow quickly, it can be challenging to treat if it spreads beyond the skin.

Program Highlights

UT Southwestern’s Comprehensive Melanoma and Skin Cancer Program specialists offer patients a unique level of expertise and experience and the most innovative and advanced therapies.

Our experts diagnose and treat all types of skin cancer – from the most common to the very rare – and deliver the advanced screening, precise diagnostics, and pioneering treatments that are leading to better-than-ever patient outcomes. UT Southwestern’s team works closely with patients to develop tailored care plans that are based on each person’s unique condition, overall health, and treatment goals and preferences.

Highlights of our program include:

  • An integrated, multidisciplinary team that includes dermatologists, surgical and radiation oncologists, medical oncologists, pathologists, and radiologists – all of whom take a personalized, evidence-based approach to skin cancer diagnosis and care
  • A focus on screening, early detection, and accurate diagnoses – all key to successful skin cancer treatment
  • The most sophisticated diagnostic tools available, including highly specialized dermatopathology testing and in-house molecular profiling
  • Expertise in all types of surgery to remove all types of skin cancer, including Mohs surgery, tumor excision, and regional lymph-node dissection 
  • Leadership in the use of stereotactic radiosurgery – including tools such as the Gamma Knife and CyberKnife – to treat some cases of skin cancer
  • Immunotherapies, such as immune checkpoint inhibitors, which stimulate the immune system to target and kill skin cancer cells
  • Targeted therapies, which use drugs to target abnormal proteins in tumor cells
  • Opportunities for patients to enroll in clinical trials aimed at improving the diagnosis and treatment of skin cancer via promising new protocols that are not yet available to the public
  • A comprehensive variety of cancer support services

Symptoms

While Merkel cell carcinoma often presents as a painless single pink, red, or purple lump on sun-exposed skin – especially the face, neck, arms, and legs – it can arise anywhere on the body. The skin on top of the lump might break open and bleed.

Risk Factors

As with all types of skin cancer, sunlight and tanning-bed exposure are key risk factors for Merkel cell carcinomas. Other risk factors include:

  • Infection with Merkel cell polyomavirus (MCV): The cells of most Merkel cell carcinomas show evidence of MCV, a common virus that most people eventually contract.
  • Gender: Men are at greater risk than women for developing Merkel cell carcinoma.
  • Fair skin: This cancer is much more prevalent among Caucasians (more than 90 percent of cases) than other races.
  • Advancing age: More than 90 percent of people diagnosed with the condition are older than age 50, and nearly 70 percent are age 70 or older.
  • Weakened immune system: Certain medical conditions and drugs weaken the immune system, increasing people’s risk for developing cancer.
  • Psoralens and ultraviolet light (PUVA) therapies: Used to treat psoriasis, these therapies can increase patients’ risk of skin cancer.

Diagnosing and Staging Merkel Cell Carcinoma

Diagnosis

UT Southwestern’s skin cancer specialists offer the following tests to evaluate and diagnose Merkel cell carcinoma. All diagnostic tests help us determine the most appropriate, evidence-based course of treatment. Tests include:

  • Medical history and physical exam
  • Skin biopsy: If a spot on the skin appears to be cancerous or precancerous, a small sample of the suspicious tissue is removed for microscopic evaluation by a dermatopathologist.
  • Lymph node biopsy: Merkel cell carcinoma often spreads to nearby lymph nodes in the early stages of the disease. If this is suspected, a small sample of the nearest lymph node might be removed for microscopic evaluation.
  • Additional testing: If the presence of Merkel cell carcinoma in a biopsy cannot be confirmed, additional testing – including an immunohistochemistry (IHC) study – might be conducted.
  • Imaging: Technologies such as computed tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), and X-rays might be used to determine if Merkel cell carcinoma has spread to other parts of the body.

Staging

Our physicians determine Merkel cell carcinoma’s stage – the severity and extent to which it has metastasized beyond the primary location – by considering these factors:

  • Extent of the tumor (T): Refers to the tumor’s location, size, and whether it has grown into nearby structures or tissues
  • Spread to nearby lymph nodes (N): Refers to whether the cancer has metastasized to lymph nodes near the tumor
  • Spread to distant sites (M): Refers to whether the cancer has metastasized to other parts of the body

Numbers or letters after T, N, or M provide more details about each of these factors of the Merkel cell carcinoma. That information is then combined with the following to determine the cancer’s overall stage:

  • Stage 0 (in situ): Pre-carcinoma that has the potential to become carcinoma
  • Stage I: Early, localized disease with no Merkel cell carcinoma in the lymph nodes
  • Stage II (IIA or IIB): Fairly early, fairly localized disease that is slightly more advanced than stage I, with no Merkel cell carcinoma in the lymph nodes
  • Stage III (IIIA or IIIB): Disease that has spread to areas in the skin near the primary location or the lymph nodes near the Merkel cell carcinoma
  • Stage IV (metastatic): Disease that has spread via the lymph nodes or the blood stream to distant parts of the body – most commonly the lungs, liver, bones, and brain

Treatments

UT Southwestern offers a number of advanced treatments for patients with Merkel cell carcinoma. They include surgery, chemotherapy, immunotherapy, and radiation therapy.

Surgery

Surgery is typically the first line of treatment for MCC, and it might be performed in combination with other therapies.

The incision and scar size, patient recovery time, and whether the surgery is performed as an inpatient or outpatient procedure all depend upon the cancer’s size, depth, and location.

UT Southwestern offers Merkel cell carcinoma surgeries that include:

  • Traditional tumor excision: Called wide excision, this surgery involves removal of the tumor and a bit of normal surrounding tissue to check for carcinoma cells. The amount of normal surrounding tissue varies by the cancer location.
  • Sentinel lymph-node biopsy: This biopsy of the adjacent lymph nodes is often performed during tumor excision surgery to see if the cancer has spread. Your surgeon will determine if you need this.
  • Regional lymph-node dissection: If the cancer has spread to the lymph nodes near the area of the MCC, your surgeon might need to remove a large number of nodes and examine them for the presence of carcinoma.
  • Mohs surgery: Used most often in non-melanoma skin cancers, this outpatient procedure removes skin cancer one layer at a time and can be used as an alternative to wide excision surgery. As each layer is removed, it’s examined under a microscope. If the margins are cancer free, the surgery is completed. This process allows surgeons to spare as much tissue as possible.
  • Reconstructive surgery: UT Southwestern surgeons can sometimes use reconstructive surgery to prevent or treat scarring or disfigurement after skin cancer treatment, especially when a tumor is large. We also offer immediate local tissue reconstruction after Mohs surgery.

Chemotherapy

Chemotherapy drugs might be used to kill MCC cells that have spread to other organs. Agents commonly used to treat Merkel cell carcinoma include cisplatin, carboplatin, etoposide, and topotecan.

Immunotherapy

Also known as biologic therapies, immunotherapies are state-of-the-art treatments that stimulate the body’s immune system to target and kill MCC cells.

UT Southwestern skin cancer specialists might use immune checkpoint inhibitor therapy – a type of immunotherapy – to treat some cases of Merkel cell carcinoma.

T cells, a type of white blood cell, are part of the immune system. When a T cell encounters an abnormal cell, it seeks to destroy it while leaving normal cells alone.

A checkpoint is when a T cell “decides” whether another cell is abnormal. MCC cells can trick T cells into “thinking” they are normal, and as a result, the immune system doesn’t fight them.

Immune checkpoint inhibitor therapy seeks to block MCC cells from turning off the T cells, which helps the T cells to better kill the cancer.

UT Southwestern offers PD-L1 inhibitors such as avelumab and PD-1 inhibitors such as pembrolizumab for the treatment of Merkel cell carcinoma.

Patients receive the drugs intravenously and must be closely monitored by their physicians for side effects. It can take six to 12 weeks for checkpoint inhibitor therapies to take effect.

Radiation Therapy

Radiation therapy uses external radiation – delivered by beams of high-energy X-rays – to target and destroy Merkel cell carcinoma cells and prevent them from growing.

UT Southwestern offers both traditional radiation therapy and stereotactic radiosurgery to treat MCC that has spread to the brain or other organs that can’t be treated with surgery or when a patient isn’t healthy enough for surgery. It might also be used after surgery to kill tumor cells left behind.

Our stereotactic radiosurgery tools include the Gamma Knife, which uses beams of highly focused gamma rays from hundreds of different angles that converge at the tumor, and the CyberKnife, a linear accelerator mounted on a robotic arm that moves around the head to focus multiple beams of radiation into the tumor.

UT Southwestern physicians and physicists are recognized as worldwide leaders in these sophisticated treatments.

Support Services

UT Southwestern’s Harold C. Simmons Comprehensive Cancer Center offers a comprehensive range of support services to help our patients and their loved ones through skin cancer treatment and beyond.

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