Figure 1.

A/C: Axial fused [⁸⁹Zr]Zr-Df-IAB22M2C PET/MRI and MRI of a metastasis with intense tracer uptake in the right gluteal subcutaneous tissue of Patient 1 after three cycles of ipilimumab until 6 weeks before the scan. B/D: Coronal fused [⁸⁹Zr]Zr-Df-IAB22M2C PET/MRI and MRI of a pararenal metastasis of Patient 1 without relevant tracer uptake after ipilimumab treatment. E-I: The pararenal metastasis of Patient 1 (red star) was resected. Histopathological analysis revealed monotonous cell proliferation in the metastasis (E). Immunohistochemistry revealed some areas with dense infiltrates of CD8⁺ T cells in the margin of the lesion (F); magnification (G), mild infiltration of CD8⁺ T cells in the center of the metastasis (focally moderate around the necrotic areas) was observed (H); magnification (I). Scale bar: 1 mm for both H&E and CD8 immunohistochemistry images.