Increased Uptake of 68Ga-Pentixafor in Thymic Rebound After Chemotherapy in a Patient With Multiple Myeloma.

A 38-year-old man with newly diagnosed multiple myeloma underwent Ga-pentixafor PET/CT for baseline assessment. Ga-pentixafor PET/CT demonstrated multiple focal bone and bone marrow lesions with intense radioactivity. After 9 cycles of chemotherapy against multiple myeloma, the patient experienced serologically complete remission of myeloma. Consistently, the follow-up Ga-pentixafor PET/CT for PET response showed significantly reduced uptake in the previously chemokine receptor 4-positive bone lesions. However, intense and homogeneous uptake of Ga-pentixafor was noted in the thymus with a smooth contour and slightly increased density, which is possibly caused by thymic hyperplasia after chemotherapy.