Merkel cell carcinoma (MCC), or neuroendocrine carcinoma of the skin, is an uncommon and often aggressive malignancy that has a poor prognosis. More than 400 new cases of MCC occur in the United States each year, and the mortality rate is approximately 25%.[1] MCC is predominantly a tumor of the elderly, and most reported cases have occurred in whites.[2-6] It occurs most frequently in the head and neck region and the extremities, and has a predilection for the periocular region.[2,3,5,6] People treated with methoxsalen and ultraviolet A for psoriasis and people who are immunocompromised have an increased incidence of developing MCC.[7]

The Merkel cell is located in or near the basal layer of the epidermis and is closely associated with terminal axons.[2,3,8] While MCC may be difficult to diagnose, it usually presents as a painless, indurated, solitary dermal nodule with a slightly erythematous to deeply violaceous color. MCC frequently involves regional lymph nodes (10% to 45% at initial presentation),[2-5,9] and between 50% and 75% of patients will develop regional lymph node metastases at some time during the course of their disease.[2-4] Distant metastases eventually occur in up to one half of patients, with lymph nodes, the liver, bone, brain, lung, and skin the most common sites of distant involvement.[2,3,5,6,10] MCC may progress rapidly, similar to aggressive melanoma. After primary tumor excision, local recurrence develops in 25% to 44% of patients; this has been attributed to inadequate surgical margins.[2,4,5]

References

1. Nghiem P, McKee PH, Haynes HA: Merkel cell (cutaneous neuroendocrine) carcinoma. In: Sober AJ, Haluska FG, eds.: Skin Cancer. Hamilton, Ontario: BC Decker Inc., 2001., pp 127-141. 
   
   
2. Haag ML, Glass LF, Fenske NA: Merkel cell carcinoma. Diagnosis and treatment. Dermatol Surg 21 (8): 669-83, 1995.  [PUBMED Abstract]
   
   
3. Ratner D, Nelson BR, Brown MD, et al.: Merkel cell carcinoma. J Am Acad Dermatol 29 (2 Pt 1): 143-56, 1993.  [PUBMED Abstract]
   
   
4. Yiengpruksawan A, Coit DG, Thaler HT, et al.: Merkel cell carcinoma. Prognosis and management. Arch Surg 126 (12): 1514-9, 1991.  [PUBMED Abstract]
   
   
5. Goepfert H, Remmler D, Silva E, et al.: Merkel cell carcinoma (endocrine carcinoma of the skin) of the head and neck. Arch Otolaryngol 110 (11): 707-12, 1984.  [PUBMED Abstract]
   
   
6. Gollard R, Weber R, Kosty MP, et al.: Merkel cell carcinoma: review of 22 cases with surgical, pathologic, and therapeutic considerations. Cancer 88 (8): 1842-51, 2000.  [PUBMED Abstract]
   
   
7. Lunder EJ, Stern RS: Merkel-cell carcinomas in patients treated with methoxsalen and ultraviolet A radiation. N Engl J Med 339 (17): 1247-8, 1998.  [PUBMED Abstract]
   
   
8. Gould VE, Moll R, Moll I, et al.: Neuroendocrine (Merkel) cells of the skin: hyperplasias, dysplasias, and neoplasms. Lab Invest 52 (4): 334-53, 1985.  [PUBMED Abstract]
   
   
9. Tai PT, Yu E, Winquist E, et al.: Chemotherapy in neuroendocrine/Merkel cell carcinoma of the skin: case series and review of 204 cases. J Clin Oncol 18 (12): 2493-9, 2000.  [PUBMED Abstract]
   
   
10. Marks ME, Kim RY, Salter MM: Radiotherapy as an adjunct in the management of Merkel cell carcinoma. Cancer 65 (1): 60-4, 1990.  [PUBMED Abstract]
    
    

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