Wolf isotopic response: immunotherapy-related lichenoid eruption localizing to prior radiation site.

Wolf isotopic response refers to a new skin disorder manifesting in the area of a previous skin lesion that has healed. A variety of disease processes and dermatoses have been described that evoke an isotopic response. We report a man with metastatic hepatocellular carcinoma who received palliative radiation and later experienced a pembrolizumab-induced lichenoid dermatitis at the same site of radiation, representing a cutaneous immune-related adverse event displaying an isotopic response.