Merkel Cell Carcinoma

What it is

Overview

Merkel cell carcinoma (MCC) is a rare but highly aggressive form of skin cancer that arises from Merkel cells — mechanoreceptors in the skin involved in touch sensation. About 80% of cases are caused by the Merkel cell polyomavirus (MCPyV). MCC has a recurrence rate of about 40% and is three to five times more likely to be fatal than melanoma.

Biology

How It Develops

MCPyV integrates into the host genome and expresses viral oncoproteins (Large T antigen and Small T antigen) that inactivate RB1 and drive proliferation. In virus-negative cases (20%), UV-induced mutations in TP53 and RB1 are the predominant drivers. Immunosuppression dramatically increases risk, as the immune system normally controls MCPyV.

Warning signs

Symptoms

• —Flesh-colored or bluish-red painless nodule, usually on sun-exposed skin
• —Rapid growth of a skin lesion
• —Lesion on the head, neck, or arms (most common sites)

Detection

Diagnosis Methods

• —Skin biopsy with immunohistochemistry (CK20 staining)
• —MCPyV serology
• —Sentinel lymph node biopsy
• —CT, MRI, or PET for staging

Medical care

Treatment Options

• —Wide surgical excision
• —Sentinel lymph node biopsy and regional lymph node dissection
• —Radiation therapy (adjuvant or definitive)
• —Immunotherapy (avelumab, pembrolizumab — FDA-approved for advanced MCC)
• —Chemotherapy (for patients unable to receive immunotherapy)

Data

Statistics

Prevention

Risk Factors

• —Advanced age (>70)
• —Immunosuppression (organ transplant, HIV, CLL)
• —Extensive UV radiation exposure
• —Light skin tone

Further reading

Resources