Merkel cell carcinoma (MCC) is a rare aggressive primary cutaneous neuroendocrine tumour. Most cases in immunocompetent patients are associated with:

• A HPV types 16 and 18
• B EBV reactivation
• C Merkel cell polyomavirus (MCPyV) ✓
• D Ultraviolet B (UVB) radiation only

Explanation

Merkel cell polyomavirus (MCPyV) is integrated clonally in approximately 80% of MCC tumours in immunocompetent patients. In MCPyV-positive tumours, viral T-antigen expression drives oncogenesis. The remaining 20% (UV-related, especially in elderly/immunosuppressed) show high mutational burden from UV signature mutations but lack MCPyV integration. MCPyV-positive tumours generally have better prognosis. Avelumab (anti-PD-L1) is the first approved immunotherapy for metastatic MCC, reflecting high immune checkpoint expression in this cancer.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.