Subsequent CD8 PET/CT imaging, performed 1 mo after the 18F-FDG PET/CT, demonstrated marked 89Zr-Df-IAB22M2C activity in both metastases (SUVMAX of 5.4 and 14.6) (Fig. 3), suggesting that the tumor had a high degree of CD8+ leukocyte infiltration; follow-up imaging over the next 6 mo supported the possibility this reflected a productive antitumor immune response because the patient experienced stable disease in these lymph nodes. This evidence concerns the gene CD8A and neoplasm.