PET/CT scan of the chest at 3 time points. (A) Whole body anterior projection image from FDG PET/CT scan at diagnosis. Red arrow points to the FDG-avid left-sided chest wall mass. Sites of soft tissue uptake in both thighs represent injection sites from recent immunizations. Transverse fusion PET/CT sections through the thorax at baseline (B-C), following upfront standard therapy with vinblastine and steroids (D-E), and after therapy with dasatinib (F-G). At baseline, the mass extends into the subcutaneous fat of the left chest wall anteriorly and abuts the pericardium (C). The response to standard therapy was suboptimal with only mild reduction in size and FDG uptake (D-E). (G) Marked reduction in size as well as FDG avidity in response to dasatinib therapy. Yellow arrows point to sites of pleural thickening that were not FDG avid (1.4 × 1.8 cm). Note that the appearance of the pleural thickening did not change after standard therapy, but nearly resolved following dasatinib. Red arrows point at the large left-chest-wall mass centered at the left anterior fourth and fifth ribs and causing rib destruction.