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 and Dermatopathology

Reviewed/Revised Sep 2022

Merkel cell carcinoma is a rare, aggressive skin cancer that tends to affect older White people. Diagnosis is by biopsy. Treatment typically is determined by staging.

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 Melanoma Malignant melanoma arises from melanocytes in a pigmented area (eg, skin, mucous membranes, eyes, or central nervous system). Metastasis is correlated with depth of dermal invasion. With spread... read more Melanoma ). Lymphatic spread is common.

Symptoms and Signs of Merkel Cell Carcinoma

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).

Diagnosis of Merkel Cell Carcinoma

  • Biopsy

Diagnosis of Merkel cell carcinoma is by biopsy.

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

Treatment of Merkel Cell Carcinoma

  • 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.

Systemic therapy (eg, with avelumab or another programmed death receptor 1 [PD-1] inhibitor or conventional chemotherapy) may be indicated for metastatic or recurrent cancer.

Prevention of Merkel Cell Carcinoma

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

Drugs Mentioned In This Article

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