The utility of positron emission tomography/computed tomography in the staging of extranodal natural killer/T-cell lymphoma

Natural killer (NK)/T-cell lymphoma cases are rarely discovered using positron emission tomography/computed tomography (PET/CT). We compared the utility of PET/CT and that of conventional methods (CMs; CT with IV contrast, biopsies from primary sites, and bone marrow examinations) in the staging of extranodal NK/T-cell lymphoma. Nineteen untreated patients with extranodal NK/T-cell lymphoma at three institutions were analyzed. PET/CT and CMs were applied for initial workups following diagnosis. PET/CT and CMs were compared and evaluated for their ability to detect tumor lesions and their influence on the staging and treatment strategies. In total, 116 lesions were detected by CM and PET/CT. Using PET/CT, 108 lesions (93%) were discovered. The number of nodal lesions was 28: all were positive by PET/CT and 26 (93%) by CMs. The number of extranodal lesions was 89: 84 (94%) and 54 (61%) lesions were positive by PET/CT and CMs, respectively. PET/CT was superior to CMs in detecting cutaneous lesions [31/31 lesions (100%) vs. 20/31 lesions (65%), respectively; P=0.042]. Bone marrow involvement was confirmed pathologically in only seven patients; four cases (57%) were positive by PET/CT. Using CMs, ten patients (53%) were stages I-II and nine (47%) were stages III-IV. Using PET/CT, eight patients (42%) were in stages I-II and 11 (58%) were in stages III-IV. PET/CT findings altered the stage and treatment strategy in two cases (11%). Our study demonstrated that PET/CT is a useful tool for detecting extranodal lesions in NK/T-cell lymphoma, particularly cutaneous lesions. PET/CT may therefore influence future staging and treatment strategies.