Merck Manual

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Merkel Cell Carcinoma

(Neuroendocrine Skin Carcinoma; Primary Small Cell Skin Carcinoma; Trabecular Cell Carcinoma; APUDoma of the Skin; Anaplastic Skin Cancer)


Gregory L. Wells

, MD, Ada West Dermatology, St. Luke’s Boise Medical Center, and St. Alphonsus Regional Medical Center

Last full review/revision Mar 2019| Content last modified Mar 2019
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Merkel cell carcinoma is a rare, aggressive skin cancer that tends to affect older white people.

Mean age at diagnosis is about 75. Merkel cell carcinoma also affects younger patients who are immunosuppressed. Other risk factors include cumulative exposure to ultraviolet light, exposure to the Merkel cell polyomavirus, and having another cancer (eg, multiple myeloma, chronic lymphocytic leukemia, melanoma). Lymphatic spread is common.

Symptoms and Signs

Skin lesions are typically firm, shiny, flesh-colored or bluish-red, and nodular. Their most characteristic clinical findings are rapid growth and absence of pain and tenderness. Although Merkel cell carcinoma can affect any part of the skin, it is most common on sun-exposed areas (eg, face, upper extremities).


  • Biopsy

Diagnosis of Merkel cell carcinoma is by biopsy.

Most patients have metastatic disease at presentation, and the prognosis is poor.


  • Determined by staging

Treatment of Merkel cell carcinoma is determined by cancer staging and typically includes wide local excision, often followed by radiation therapy, lymph node dissection, or both.

Chemotherapy may be indicated for metastatic or recurrent cancer.


Because Merkel cell carcinoma seems to be related to ultraviolet (UV) exposure, a number of measures are recommended to limit exposure.

  • Sun avoidance: Seeking shade, minimizing outdoor activities between 10 am and 4 pm (when sun's rays are strongest), and avoiding sunbathing and the use of tanning beds

  • Use of protective clothing: Long-sleeved shirts, pants, and broad-brimmed hats

  • Use of sunscreen: At least sun protection factor (SPF) 30 with broad-spectrum UVA/UVB protection, used as directed (ie, reapplied every 2 hours and after swimming or sweating); should not be used to prolong sun exposure

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