(See also Overview of Skin Cancer.)
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.
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).
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.
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