Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, highly aggressive skin cancer affecting older patients, and thought to arise from the cutaneous Merkel cell, a neuroendocrine cell. MCC has a high propensity for local recurrence, as well as regional and distant metastases. Mortality rates of 30-50% have been reported.

This chapter is set out as follows:

• The exact cause of MCC is not known

• Factors strongly associated with the development of MCC are:
• Age over 65 years
• Fair skin
• History of extensive UV exposure
• Chronic immunosuppression (eg kidney or heart transplantation, HIV)

• MCC has recently been linked to a virus (Merkel cell polyomavirus), which most adults have been exposed to during their lifetimes. It is thought that an interaction of the viral DNA and ultraviolet light can lead to formation of this cancer later in life

• The best available information on the characteristics of patients with MCC comes from a study of 1,034 patients (Agelli, 2003), which showed the average age of presentation was 74 years

• Lesions tend to be asymptomatic and can grow very quickly

Distribution 

• The most common sites are the head and neck followed by the arms

Morphology

• Lesions do not have a distinctive appearance
• They tend to arise as firm, shiny, raised intradermal nodules that vary from red to violet ​
• Ulceration is uncommon 
• The size varies from 1-5 cm in diameter 

• Patients must be referred urgently to Secondary Care (two-week wait)

• The treatment of choice for the primary lesion in MCC is surgical excision. Because of the high propensity for local recurrence, wide local excision including 2-3 cm of normal-appearing skin is the standard recommendation for reducing the incidence of recurrence

• Early detection and intervention is essential - a recent study showed that patients who have no lymph node disease as detected by sentinel lymph node biopsy (SLNB) or other lymph node surgery have a much better prognosis