Merkel cell carcinoma is a rare neuroendocrine skin cancer that was first described in 1972. It is most commonly associated with Merkel cell polyomavirus infection and/or mutagenesis from chronic exposure to ultraviolet light. The population at risk includes the elderly and immunosuppressed people, such as those with organ transplantation and HIV infection. The incidence of Merkel cell carcinoma in the United States is around 0.79 per 100,000 people; however, the highest incidence is found in Australia, 1.6 per 100,000 people.(1)
How Dangerous Is Merkel Cell Carcinoma?
The estimated mortality associated with Merkel cell carcinoma is around 33-46% that has significantly increased in recent times. It is a very aggressive tumor and nearly 33% of patients die due to it that makes it twice as fatal as melanoma. It is also the second leading cause of death due to skin cancer after melanoma. Although there have been major advances in the understanding of the tumor, the survival rates are still low, 5-year survival for advanced-stage cancer is 0-18%. Since there is still lack of appropriate choice of treatment for advanced Merkel cell carcinoma and the treatment is largely dependent on the location of tumor and comorbidities, there is still need for effective treatment options that are safe and tolerable.(1)
Advancing age, male sex, vitamin D deficiency and immunosuppression are associated with poorer prognosis. The survival rate is reduced in the presence of immunosuppression and associated comorbidities. Since, Merkel cell carcinoma is associated with increased risk of recurrence and secondary malignancies such as malignant melanoma, chronic lymphocytic leukemia, and other hematologic malignancies; the overall survival is further reduced. Approximately 37% of people at the time of diagnosis present with nodal disease and about 6-12% of patients present with distant metastasis. The metastasis of tumor is common and observed within 3 years of diagnosis. Metastasis mostly occurs in the draining lymph node basins, followed by distant skin, lung, central nervous system, bone, and liver.(1)
Is Merkel Cell Carcinoma Contagious?
Although Merkel cell carcinoma can be caused by infections, such as bacteria, parasites, and viruses, the cancer is not contagious. Merkel cell polyomavirus that is found in 80% of the patients with Merkel cell carcinoma is a virus that normally inhabits the human body and asymptomatic infection with the organism is very common. The virus is typically acquired in childhood. However, Merkel cell carcinoma is a very rare form of cancer as compared the number of individuals infected with polyomavirus and majority of the individuals infected with the virus do not develop the tumor. The virus can be transmitted from one individual to another, but cancer cannot be transmitted.(2)
Clinical Presentation Of Merkel Cell Carcinoma
Merkel cell carcinoma presents as a painless, indurated and rapidly enlarging red-violet nodule shaped like a dome. The nodules are frequently found in the area of sun exposure, such as head, neck and upper extremities. For better clinical identification and assistance in initial diagnosis the acronym AEIOU is used, which signifies asymptomatic (lack of tenderness), expanding rapidly, immunosuppression, older age >50 years, and UV exposed site on a person with fair skin.(1)
Cause Of Merkel Cell Carcinoma
Merkel cell carcinoma is caused by mutations in the DNA of the cells. The mutations in the cell lead to increased uncontrolled replication and division of the cells into new cells. The mutations, however, are not inherited from parents and are a result of somatic mutations during a person’s lifetime. In some cases, the cause of mutations is unclear; however, most of the cases are associated with increased and chronic exposure to sunlight and Merkel cell polyomavirus. Other risk factors include older age >50 years, fairer skin and chronic immune suppression such as organ transplantation and HIV infection.(2)