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

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

T. Primary Tumor N. Regional Lymph pN. Regional Lymph M. Distant Metastasis
  Nodes Nodes-Pathologic Evaluation  
Tx. Primary tumor cannot be assessed Nx. Clinical assessment cannot be done pNx. Assessment cannot be done M0. No distant metastasis
Tis. In situ primary tumor N1. Clinically detected regional metastasis pN1a(sn). Nodal metastasis identified by sentinel lymph node biopsy M1a. Metastasis to distant skin, subcutaneous tissue or lymph nodes
T1. Primary tumor ≤2 cm   pN1a. Lymph node dissection shows metastasis M1b. Lung
T2. Primary tumor >2 cm but ≤5 cm   pN1b. Lymph node metastasis detected clinically or radiologically, microscopically confirmed M1c. All other distant sites
T3. Primary tumor >5 cm N2. In-transit metastasis without lymph node metastasis pN2. In-transit metastasis without lymph node metastasis  
T4. Primary tumor invades fascia, muscle, cartilage or bone N3. In-transit metastasis with lymph node metastasis pN3. In-transit metastasis with lymph node metastasis  


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Sheetal DeCaria MD

Written, Edited or Reviewed By:


Last Modified On: August 1, 2019

This article does not provide medical advice. See disclaimer


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