Merkel Cell Carcinoma Case 1 Merkel cell carcinoma
By Simon Naseri, MD, Mike Mikkelsen Lorenzen, MD and Magnus Balslev Avnstorp, MD
Merkel cell carcinoma, first described in 1972 by Toker, is a rare and aggressive neuroendocrine carcinoma of the skin. MCC is caused by UV-radiation (in 24 %) and/or the merkel cell polyoma virus (MCV, in 76 %). The incidence of MCC is 0.22 per 100’000 person years (1995-2006). Risk factors for developing MCC include immunosuppression, as seen in patients with chronic lymphatic leukemia (30-fold increase), the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS, 13-fold increase) and organ transplants recipients (10-fold increase). Patients diagnosed with MCC have a 5-year overall survival of 40 %, making it more deadly than melanoma.
MCC is characterized by its aggressive local growth and high rate of metastasis, as 35 % of patients initially present with metastatic disease. Merkel cell polyomavirus is responsible for 74 % of MCCs and induce carcinogenesis by incorporating its viral DNA into the host DNA. The viral DNA encodes oncoproteins that inhibit tumor suppressor function and initiates carcinogenesis.
Treatment and surgical margins
All MCC-patients should be evaluated individually in multidisciplinary tumor board consultations.
Primary tumor management
- Radical excision with a margin of 1-2 cm to the fascia.
- Adjuvant radiotherapy (RT) is recommended in patients with:
- Large primary tumor (> 1 cm diameter)
- Lymphovascular invasion
- Chronic immunosuppression (i.e., lymphoma/leukemia)
- Positive excision margin status
- Positive sentinel lymph node biopsi
Regional lymph node involvement
- Therapeutic radical lymph node dissection is recommended in case of lymph node involvement
- Adjuvant radiotherapy may be considered in case of extracapsular disease.
Distant metastatic disease
- Immunotherapy with PD/PD-L1 inhibitors such as avelumab and pembrolizumab are recommended as first-line treatment.
- Chemotherapy with cisplatin or carboplatin in combination with etoposide is recommended as second-line treatment.