FIGURE 5.  (A and B) One day after RFA, coronal PET image (A) shows completely ablated VX2 and ring-shaped accumulation of ¹⁸F-FDG (arrow) around site of RFA. Histopathologic specimen (x40, B) shows VX2 necrosis and outer-zone tissue congestion and inflammatory cell infiltration. Comparison with PET image indicates that inner necrotic zone corresponds to ablated tumor mass, whereas outer inflammatory layer corresponds to ring-shaped ¹⁸F-FDG accumulation. (C) High-power (x400) view of histopathologic specimen shows blurred cytoplasmic borders, pyknotic nuclei, and blurred chromatins—characteristic features of ongoing necrosis. O = outer zone; T = VX2.