What is Merkel Cell Carcinoma?

A rare type of skin cancer, Merkel cell carcinoma (MCC) often looks like a cyst, pimple, or stye. It can even be mistaken for an insect bite. While this red to violet-colored growth may look harmless, it is very aggressive. MCC tends to spread quickly. Learning the signs and symptoms can help you spot MCC early when it is most treatable.

Signs and Symptoms of Merkel Cell Carcinoma
Until recently, common signs and symptoms of MCC were not defined. To identify common characteristics of MCC, a team of physicians studied 195 patients diagnosed with MCC between 1980 and 2007. These common characteristics emerged:

The AEIOUs of Merkel Cell Carcinoma

The Lesion

  • Asymptomatic. Growth does not feel tender or painful. (88%)

  • Expands (grows) rapidly. The lesion/spot grows quickly. (63%)

The Person

  • Immune system may be weakened. The person’s immune system can be weakened from taking medication that helps prevent organ rejection or a medical condition such as HIV. (7.8%)

  • Older than 50 years of age. Most cases are diagnosed in people aged 50 and older. (90%)

  • Ultraviolet (UV) exposure. MCC tends to develop on skin that has received years of UV exposure. (81%) When the skin is fair and has had years of UV exposure, this percentage jumps to 98%.

Source: Journal of the American Academy of Dermatology, 2008 Mar;58(3):375-81. Heath M, Jaimes N, Lemos B et al. “Clinical characteristics of Merkel cell carcinoma at diagnosis in 195 patients: the AEIOU features.”

Where Merkel Cell Carcinoma is Most Likely to Appear
Like other types of skin cancer, MCC is most likely to appear on skin that has received years of sun exposure. About 50% of MCCs occur on the head and neck. The eyelid is a common site as is the rest of the skin around the eye.

MCC is not limited to the head and neck. It can appear anywhere on the skin. A tumor may develop on an arm, leg, or buttock. MCC has even been found inside the mouth and on the genitals.

Looking very much like a bug bite, a biopsy revealed that this was Merkel cell carcinoma on the patient’s shin.

Merkel cell carcinoma developed on the scalp of this 94-year-old man.

(Photos used with permission of the American Academy of Dermatology
National Library of Dermatologic Teaching Slides)

Who is Most at Risk?
People 50 years of age or older who have fair skin and did not protect their skin from the sun are most at risk. Research also suggests that men are twice as likely as women to develop MCC.

It is rare for MCC to develop in someone under 50. If MCC develops before then, the person usually has a weakened immune system. Medication taken to prevent organ rejection after a transplant operation weakens the immune system. The risk of MCC increases 10-fold in people taking this medication. Illnesses that weaken the immune system such as HIV and chronic lymphocytic leukemia (a cancer of the blood and bone marrow) also increase the risk. While a weak immune system increases the risk, age and fair skin are still greater risk factors.

Exposure to arsenic, infrared light, and certain medications also increase the risk. One such medication is methoxsalen (meth-OX-a-len). This medication is used in UV light therapy. Some patients who have psoriasis or vitiligo receive methoxsalen during their PUVA therapy.

Rare . . . But Cases Increasing
Cases of MCC tripled between 1986 and 2001. About 1,500 cases are now diagnosed in the United States each year, so MCC is still a rare skin cancer. Researchers believe that the increase may be due to the growing number of people over 50 years of age who had years of unprotected sun exposure. As this population grows, cases of MCC may rise.

Early Treatment Offers Best Prognosis
Research suggests that early detection can improve the patient’s prognosis. If the cancer has not spread, the patient may have a greater than 90% chance of surviving.

If you believe you may have a growth on your skin that could be MCC or any other type of skin cancer, see a dermatologist. These doctors regularly diagnose and treat skin cancer.

Related Link
Merkel Cell Carcinoma: What it Looks Like

References:
Brewer JD, Appert DL, Rognigk RK. “Merkel Cell Carcinoma.” In: Nouri K, “Skin Cancer.”China. McGraw Hill Medical; 2008. p. 181-94.

Heath M, Jaimes N, Lemos B et al. “Clinical characteristics of Merkel cell carcinoma at diagnosis in 195 patients: the AEIOU features.” J Am Acad Dermatol 2008; 58:375-81.

Nghiem P, Jaimes N. “Merkel Cell Carcinoma.” In: Wolff K, Goldsmith LA, Katz SI, et al. editors. Fitzpatrick’s Dermatology in General Medicine, 7th ed. United States of America, McGraw Hill Medical; 2008. p. 1087-94.


All content solely developed by the American Academy of Dermatology

Merkel cell carcinoma is even more aggressive than melanoma, a skin cancer that claims one American life every 62 minutes. Early detection and treatment of these skin cancers is crucial.

 
 

 

 

 

 

 

 
 
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Page last updated 12/12/08

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