Merkel cell carcinoma is uncommon yet aggressive skin cancer. It was first described by Cyril Toker in 1972. It is associated with high mortality and lags behind melanoma for skin cancer-related mortality, although it accounts for less than 1% of all malignant skin tumors. Although Merkel cell carcinoma is an aggressive tumor, it can be cured if it is diagnosed at an early stage and treated at an appropriate time.(1)
The global annual incidence of Merkel cell carcinoma is around 0.13-1.6 per 100,000 persons and it seems to be increasing. Merkel cell carcinoma is a disease of the elderly and usually affects individuals in their seventh and eighth decade of life with approximately 5% people aged <50 years being affected. It is extremely rare in children and more common in whites and in men than in women. People with Merkel cell carcinoma have a higher propensity for other skin tumors and it has a strong association with chronic lymphocytic leukemia.(1)
Life Expectancy Of Someone With Merkel Cell Carcinoma
According to the American Joint Committee on Cancer, Merkel cell carcinoma can also be classified as:
Stage 0: in situ
Stage I: a localized disease with primary lesion ≤2 cm
Stage II: a localized disease with primary lesion >2 cm
Stage III: nodal spread
Stage IV: metastatic disease beyond the local nodes
The life expectancy of a patient with Merkel cell carcinoma is dependent on the stage of the disease at the time of diagnosis. The 5-year survival for stage I cancer is 62.8%, stage II is 34.8-54.6%, stage III is 26.8-40.3% and for the stage, IV is 13.5%.(2)
The nodal metastases are seen in about 30% of the patients at the time of diagnosis and in >80% of patients over the course of the disease. The life expectancy of a patient is also affected by the number of lymph nodes affected. The 5-year survival of a patient with 0 lymph nodes affected is 76%; 1 lymph node, 50%; 2 lymph nodes, 47%; 3-5 lymph nodes, 42%, and more than 6 lymph nodes, 24%.(1)
Merkel cell carcinoma is found in individuals with chronic UV exposure as >50% of the lesions are found in sun-exposed areas, such as head, neck, and arms.
Immunosuppression (organ transplant, HIV infection, lymphoproliferative cancers) and Merkel cell polyomavirus infection are major risk factors for Merkel cell carcinoma. Arsenic poisoning is also related to a higher chance of Merkel cell carcinoma.(1)
Merkel cell carcinoma presents as a painless, red-violet or red-blue colored solitary and firm rapidly growing mass. It is easily confused with benign lesions or other tumors that leads to delayed diagnosis. The acronym, AEIOU for asymptomatic, expanding rapidly, immunosuppression, older age (>50 years), and UV radiation exposure assists in diagnosis. However, confirmatory diagnosis is made based on biopsy results.(1)
The risk of recurrence and mortality is high in Merkel cell carcinoma, so it is important to have sentinel lymph node biopsy for the staging of cancer as it first spreads in the regional lymph nodes.(1)
TNM Staging by American Joint Committee on Cancer for Merkel cell carcinoma
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