Clinical Significance of Incidental 18F-FDG Uptake in the Pyriform Sinus Detected by PET/CT

Purpose We investigated the significance of unexpected focal pyriform sinus FDG uptake and determined the ability of PET/CT parameters to identify malignancy. Materials and Methods FDG PET/CT reports of 56,585 consecutive infjects were retrospectively reviewed, and 281 cases (0.50%) with focal pyriform sinus uptake were included. PET images were assessed for maximum standardized uptake values (SUV_max) and asymmetric indices of FDG activity, and CT images were evaluated for pyriform sinus narrowing. The final diagnosis was determined by tissue biopsy, laryngoscopy, radiological findings, and clinical follow-up. Results Among the 281 infjects, final diagnosis was pyriform sinus malignancy in 29 (10.3%) and benignity in 215 cases (76.5%). Malignant lesions had significantly higher SUV_max (9.13 ± 3.64 vs. 3.53 ± 1.01) and asymmetric index (4.16 ± 1.81 vs. 1.54 ± 0.39) compared to benign causes. Patients with malignant lesions also had higher cervical lymph node SUV_max (6.66 ± 8.79 vs. 2.76 ± 2.46, all P < 0.001). Lesion SUV_max ≥4.24 identified malignancy with a sensitivity of 93.1% and specificity of 86.5%. Asymmetric index ≥1.81 had a sensitivity of 100% and specificity of 89.7%. Conclusion Incidentally identified focal pyriform sinus uptake on FDG PET/CT should be evaluated for possible malignancy in the presence of high SUV_max or asymmetric index.