Merkel Cell Carcinoma Facts

What Is Merkel Cell Carcinoma?

Merkel cells — which act like a combination of a nerve cell and hormone-producing cell — are located at the base of the epidermis (the outer layer of your skin). Merkel cells are connected to nerve endings that enable your sense of touch. These cells are where Merkel cell carcinomas originate.

What Causes Merkel Cell Carcinoma?

Risk factors for Merkel cell carcinoma include sun exposure, weakened immune systems and old age. Merkel cell polyomavirus also has been linked to the development of Merkel cell carcinoma.

What Are the Signs and Symptoms of Merkel Cell Carcinoma?

The most important warning sign of Merkel cell carcinoma is a shiny and painless skin tumor, called a nodule. It’s usually flesh-toned or purplish or bluish-red in color. An important warning sign is the nodule's rapid growth. It typically appears on sun-exposed areas, such as your face, head or neck. It's sometimes mistaken for basal cell carcinoma or an insect bite.

If you notice any new or unusual skin changes, contact your doctor.

What Are the Stages of Merkel Cell Carcinoma?

In early skin cancers, the tumors are small, contained within the top layers of skin and have not spread to distant organs. As the cancer progresses, the tumor grows larger and more deeply into the skin layers, spreading to lymph nodes and blood vessels and, potentially, distant organs. After Merkel cell carcinoma has been diagnosed, your skin cancer care team performs tests to find out if the cancer cells have spread to other parts of your body.

Four Stages of Merkel Cell Carcinoma

Stage 1

In Stage 1, abnormal Merkel cells have been found in the top layer of skin and spread into nearby normal tissue. At this point, the tumor is 2 centimeters or smaller.

Stage 2

In Stage 2, the tumor is either larger than 2 centimeters or it has spread to nearby connective tissue, muscle, cartilage or bone.

Stage 3

In Stage 3, Merkel cell carcinoma may have spread to lymph nodes or is in a lymph vessel between the primary tumor and lymph nodes that are near or far away.

Stage 4

In Stage 4, the tumor has spread to skin that is not close to the primary tumor or to other parts of the body, e.g., the liver, lung, bone or brain.

Merkel cell carcinoma can recur after treatment.

What Increases Your Risk of Merkel Cell Carcinoma?

The main risk factor for developing Merkel cell carcinoma is exposure to ultraviolet radiation from:

  • Sunlight
  • Tanning beds
  • Sun lamps

Other factors that may contribute to developing skin cancer include:

  • Having a history of severe, blistering sunburns
  • Having many, or unusual, moles
  • Being a blond or redhead, having fair skin that easily freckles or sunburns
  • Exposure to large amounts of toxic substances, such as paraffin oil, coal tar and arsenic compounds
  • Family history of skin cancer
  • Previously being diagnosed with skin cancer
  • Being older, male
  • Having a weakened immune system
  • Having a rare inherited condition called xeroderma pigmentosum
Skin Cancer Prevention
Skin Cancer Safety Guide

Download the sun safety guide

Ultraviolet damage is cumulative, meaning it begins building up in your childhood, so prevention should start at a young age. The best ways to lower your risk for skin cancer include shielding the skin as much as possible from UV radiation:

  • Use sunscreen and reapply at least every two hours
  • Wear protective clothing, including fabrics not easily penetrated by UV light
  • Wear other protective items such as hats and sunglasses
  • Stay in the shade during peak hours when the sun’s UV rays are most intense (from 10 a.m. to 4 p.m.)
  • Avoid tanning salons