Merkel Cell Carcinoma

Patients who experience a recurrence of their Merkel cell carcinoma are often treated aggressively. We report a case of a man with an unusually long course of MCC over 15 years who had his MCC recur around his face or neck 7 times before eventually developing distant spread. Because he had 4 major medical problems at the time his MCC initially appeared, less aggressive therapies were chosen for his recurrences, and there was no evidence of disease for the vast majority of his 15-year course, during which he enjoyed excellent quality of life. This case emphasizes the importance of customizing care in MCC to give patients the best quality and quantity of life possible in their particular situation.

The antigen specificity of T cells is conferred by the TCR’s highly variable complementarity-determining regions (CDRs), which interact with the pMHC4. Cellular immunity requires a pool of naive T cells (the T-cell repertoire) that can recognize a multitude of potential pMHC antigens that may originate from infections or cellular transformation. If a given TCR could recognize only a single combination of peptide and MHC, an individual would need >1015 CD8+ T cells to provide efficient coverage of all potential foreign peptides, whereas it is estimated that an individual has only around 107–108 different T cells5–7. The promiscuity of TCRs allows the recognition of numerous different pMHCs by each T cell, which broadens the recognition space and ensures the effective recognition of most possible targets.