Merkel Cell Carcinoma

April 10, 2026

This page was reviewed under our medical and editorial policy by Gaurav Singh, M.D., M.P.H., F.A.C.M.S., Mohs Micrographic Surgeon and Dermatologist, City of Hope^® Cancer Center Chicago.

Merkel cell carcinoma is an aggressive but rare form of skin cancer. It also has a higher-than-average risk of coming back after treatment. Around 3,000 people are diagnosed with Merkel cell carcinoma in the United States every year.

Although it is rare, Merkel cell carcinoma rates are rising, in part because of better screening and in part because it tends to affect older or immunocompromised adults — a group that has been growing over time.

What Are Merkel Cells?

Merkel cell carcinoma develops in the Merkel cells, which are among the types of cells that form the outermost layer of the skin (the epidermis). Merkel cells play a key role in sensation, helping the body detect fine detail on an object or feel light touch against the skin. Merkel cells are considered a type of neuroendocrine cell, because they are related to nerve function (“neuro”) and hormone production (“endocrine”).

What Is Merkel Cell Carcinoma?

Merkel cell carcinoma is a very rare type of skin cancer, but it’s more aggressive than other forms of the disease. It is typically fast-growing and more likely to spread (or metastasize) to other parts of the body. Merkel cell carcinoma affects about 3,000 Americans annually, with about 40% of people experiencing recurrent disease even after treatment.

“After a Merkel cell carcinoma diagnosis, patients often want to know what we’ll do next, and how we will do it” says Gaurav Singh, M.D., M.P.H., F.A.C.M.S., Mohs micrographic surgeon and dermatologist at City of Hope^® Cancer Center Chicago. “I take the time to explain how the disease occurs and discuss all treatments that could be necessary, including surgery, radiation and immunotherapy. We also use precision medicine and advanced tools such as circulating tumor DNA, which helps find cancer earlier than many other modalities such as imaging.”

What Causes Merkel Cell Carcinoma?

Merkel cell carcinoma occurs when Merkel cells in the skin start to grow out of control and form a tumor. Merkel cell carcinoma shares many of the same risk factors as more common skin cancer types, such as basal cell carcinoma or squamous cell carcinoma, such as exposure to ultraviolet light from the sun. However, some of the risk factors unique to Merkel cell carcinoma include those listed below.

Having a suppressed immune system: This condition makes it 15 times more likely someone may develop Merkel cell carcinoma and increases the chances he or she may develop it at an earlier age. Certain health conditions, such as HIV, leukemia or lymphoma, as well as medications given to organ transplant patients or those with autoimmune disorders, may suppress the body’s natural immune system.

A history of other skin cancers: Having previously had basal cell carcinoma, melanoma or squamous cell carcinoma increases a person’s chances of developing Merkel cell carcinoma.

The presence of Merkel cell polyomavirus: This type of cancer-related virus may be linked to the development of Merkel cell carcinoma, although research into the connection between the two is still underway.

Where Does Merkel Cell Carcinoma Form?

Most Merkel cell carcinoma tumors form on parts of the body that are frequently exposed to the sun. The most common location for Merkel cell carcinoma is the face, followed by the neck or the arms. Diagnosing Merkel cell carcinoma is usually performed by using a biopsy, which is a procedure to remove a small sample of tissue so that it may be examined in a lab for signs of cancer.

Merkel Cell Carcinoma Symptoms

Some common signs or symptoms of Merkel cell carcinoma include:

• A round lump or bump on the skin that is red, purple or skin-colored
• A small, shiny, pimple-like bump that grows in size quickly
• A red, purple or skin-colored bump that develops a sore that won’t heal

Does Merkel Cell Carcinoma Bleed?

Yes, Merkel cell carcinoma tumors sometimes develop an open sore or break open and heal multiple times. During this process, the tumor may bleed.

Merkel Cell Carcinoma Stages

Staging is the process of using tests to determine how advanced a patient’s cancer is, as a way to guide treatment. Merkel cell carcinoma is most often staged using the TNM staging system, which assesses the size of a tumor (T), whether the cancer has spread to nearby lymph nodes (N) and whether it has spread, or metastasized (M), to other parts of the body, as detailed below.

Stage 1: At this stage a merkel cell carcinoma tumor is no bigger than 2 centimeters (cm) and the cancer cells are confined to the topmost layer of skin.

Stage 2: Merkel cell carcinoma may have spread to nearby tissue, but not to the lymph nodes. It is larger than 2 cm across and may in some cases be larger than 5 cm in diameter.

Stage 3: Merkel cell carcinoma may have spread to nearby or distant lymph nodes. The tumor may be any size.

Stage 4: Merkel cell carcinoma has spread to nearby tissue and to distant organs or tissue. It may or may not have also spread to nearby or distant lymph nodes.

Merkel Cell Carcinoma Treatment

Treatment for Merkel cell carcinoma may involve one type of treatment only or several types in combination. Patients’ treatment plans take into account a range of factors, including the cancer’s size, stage and location, as well as the patient’s overall health.

Surgery

Skin cancer surgery is often the first treatment option for patients with Merkel cell carcinoma. One of several different types of surgery may be recommended, depending on where the tumor is located and how far it has spread. Surgical techniques used to remove Merkel cell carcinoma tumors include excision and Mohs micrographic surgery. If the cancer has spread to nearby lymph nodes, patients may also undergo a lymphadenectomy, which is surgery to remove the affected lymph nodes. Surgery may be used alone or in combination with other treatments.

Radiation Therapy

Radiation therapy uses high-powered radiation to target and destroy cancer cells. Most patients receive radiation therapy after undergoing surgery to remove Merkel cell carcinoma. The goal for these patients is to kill any remaining cancer cells and to reduce the risk of the cancer coming back. However, if the tumor is in a hard-to-reach area, radiation therapy may be the first treatment recommended by a patient’s cancer care team.

Immunotherapy

Immunotherapy refers to any type of medication that is designed to boost the body’s natural immune system or improve its immune response to cancer. An immunotherapy drug called avelumuab is sometimes used to treat Merkel cell carcinoma that has spread to other parts of the body or that has come back after initial treatment.

Merkel Cell Carcinoma Survival Rates

The American Cancer Society tracks five-year survival rates for Merkel cell carcinoma. A five-year survival rate refers to the number of patients who survive at least five years beyond their original diagnosis. Survival rates for Merkel cell carcinoma are grouped according to whether a patient’s disease is localized, meaning it has not spread beyond the tumor itself; regional, meaning it has spread to nearby tissue; or distant, meaning it has spread to distant tissue or organs.

The survival rate for:

• Localized Merkel cell carcinoma is 79%
• Regional Merkel cell carcinoma is 66%
• Distant Merkel cell carcinoma is 31%

A number of different factors may affect the prognosis for patients with Merkel cell carcinoma, including the stage and extent of their cancer, their age and overall health and whether the cancer is new or recurrent.