B-lineage p16^INK4a deletion is associated with high-grade B-cell neoplasms. (A) Representative fused PET/CT images of aged CD19^Cre/+p16^+/+ and CD19^Cre/+p16^L/L mice identifying tumors with high ¹⁸F-FDG uptake in brain (BR), spine (SP), spleen (SPL), and lymph nodes (LN). Background uptakes were observed in heart (HT), bladder (BDR), kidney (KN), and retro-orbital gland (RG). (Top) Sagittal images with red lines indicating level of the associated transverse images (bottom). (B) A T2-weighted MRI of a representative CD19^Cre/+p16^L/L mouse indicates a lesion in the spinal cord, which was confirmed by histopathologic analysis to represent lymphoma invading spinal cord from bone marrow. Original magnification ×20. (C) Hematoxylin and eosin–stained images of CNS lymphomas in the brain (top) or spinal cord (bottom) of aged CD19^Cre/+p16^L/L mice. Comparison images from littermate CD19^Cre/+p16^+/+ mice are shown (left). Original magnification ×40.