The significance of a fatty hilum within an FDG avid lymph node

1077 Objectives: A fatty hilum within a lymph node on CT is considered a benign characteristic. Yet, at times there is associated FDG activity. This study examines the nature of FDG uptake within nodes with a fatty hilum on PET/CT. Methods: 11 PET/CT scans for cancer staging that had increased FDG uptake in lymph nodes with fatty hila were retrospectively reviewed. Benign or malignant etiology were determined by clinical and imaging follow-up. 95% bootstrap confidence intervals were computed to assess the mean differences in SUVmax and short-axis nodal diameter between benign and malignant nodes. Results: Twelve lymph nodes from eleven patients with FDG uptake and fatty hila had a mean SUV of 4.7 ± 2.7 (range: 2.2 to 11.4), and a mean diameter of 1.2 cm ± 0.4 (range: 0.7 to 1.6 cm). Six lymph nodes were of malignant etiology. The mean SUV of the malignant nodes was 5.3 ± 3.7 with a mean diameter of 1.4 cm ± 0.4. Six lymph nodes were of benign etiology. Mean SUV of the benign nodes was 4 ± 1.4 with a mean diameter of 1 cm ± 0.2. Confidence intervals for the mean SUV and diameter differences are (-4.43, 1.27) and (-0.733, -0.0667), respectively. Conclusions: Hypermetabolic activity in a lymph node with a fatty hilum may be of benign or malignant etiology. The 95% confidence interval for SUV overlaps zero, indicating no evidence of a difference in SUV between benign and malignant nodes. There is weak evidence to support that malignant nodes are larger. The presence of a fatty hilum should not dissuade further investigation in the proper clinical scenario.