Additional Value of PET/CT over PET in Assessment of Locoregional Lymph Nodes in Thoracic Esophageal Squamous Cell Cancer

50-y-old man with well-differentiated squamous cell cancer of middle thoracic esophagus was referred for preoperative disease staging. (A) Maximum-intensity-projection ¹⁸F-FDG PET image shows focus of intense, inhomogeneous pathologic uptake at site of primary esophageal tumor (arrow). (B) Transaxial PET/CT image shows that intense focus of ¹⁸F-FDG uptake (SUV, 6.5) is near primary tumor (upper arrow) and defines additional focus of abnormal ¹⁸F-FDG uptake (diameter, 0.8 cm; SUV, 3.5) in paraesophageal lymph node (lower arrow), which was confirmed as lymph node metastasis of well-differentiated squamous cell cancer on pathologic examination. This focus, in close proximity to intense uptake in primary esophageal lesion, could not be identified on PET image (C) reviewed side-by-side with CT image (D). Findings on PET/CT were defined as TP, and findings on side-by-side review of PET and CT were defined as FN.