Merkel cell carcinoma (MCC) is a rare but aggressive and lethal neuroendocrine carcinoma of the skin. Merkel cell carcinoma is more common in the elderly (age greater than 65) and mainly in Caucasians. MCC rarely occurs in patients with dark skin. Vast majority of these tumors present on sun exposed sites.
What causes Merkel Cell Carcinoma?
Excessive sunlight, prolonged ultraviolet radiation exposure, and photochemotherapy are all associated with an increased risk of MCC. Immunosupression due to solid organ transplant, HIV infection or chronic lymphocytic leukemia is also associated with merkel cell carcinoma.
Recently it has been suggested that a new virus named Merkel cell polyomavirus which was found in 8 out of 10 cases of merkel cell carcinoma may play role in etiology of Merkel cell carcinoma. 
Merkel cell carcinoma usually presents as firm, raised, reddish-blue or skin colored papule or nodule. Most initial lesions are less than 20 mm in diameter which grows rapidly with in 1-3 months. Ulceration of the lesion is rare. They re usually seen on sun exposed areas but not always. They are locally aggressive and later spread to distant lymph nodes in axilla, neck and groin.
Treatment for Merkel Cell Carcinoma
The current preferred treatment is surgical excision with sentinel lymph node biopsy followed by lymph node removal if biopsy comes positive. This may be followed by radiotherapy and this approach loco-regional control and disease free survival [2, 3]. Chemotherapy is not routinely recommended.
1. Feng H, Shuda M, Chang Y et al. Clonal integration of a polyomavirus in human Merkel cell carcinoma. Science 2008; 319: 1096–100.
2. Mojica P, Smith D, Ellenhom JD. Adjuvant radiation therapy is associated with improved survival in Merkel cell carcinoma of the skin. J Clin Oncol 2007; 25:1043–7.
3. Eng TY, Boersma MG, Fuller CD et al. A comprehensive review of the treatment of Merkel cell carcinoma. Am J Clin Oncol 2007; 30: 624–36.