FDG uptake in upper abdominal lymph node as a distinctive pattern in sarcoidosis

To evaluate the distribution patterns of sarcoidosis involvement on FDG-PET/CT in patients with known or suspected cardiac sarcoidosis (CS), with a particular focus on upper abdominal lymph nodes (LN) (periportal LN [PLN], anterior pancreaticoduodenal LN [APDLN], and posterior pancreaticoduodenal LN [PPDLN]) and the association of them with other lesions and myocardium.

We identified 861 FDG-PET/CT scans performed between July 2016 and August 2024 in patients with known or suspected CS, and included 178 cases for analysis of FDG uptake patterns suggestive of sarcoid involvement. FDG-positive LNs or regions were classified as sarcoidosis-related based on treatment response, characteristic uptake patterns, or histological confirmation. The occurrence ratio of FDG-positive lymph nodes or regions was also assessed in relation to myocardial FDG uptake patterns.

FDG uptake was observed most frequently in hilar and mediastinal LNs (79% and 76%, respectively). Upper abdominal LN uptake was observed in 49.4% of patients, most commonly in the PLN (31.5%), APDLN (38.2%), and PPDLN (37.1%). Heatmap analyses revealed strong co-occurrence between thoracic and upper abdominal LNs, suggesting a lymphatic dissemination pattern. Peripheral LNs such as axillary, subclavian, and inguinal/pelvic stations demonstrated low uptake and minimal co-occurrence.

FDG-PET/CT provides valuable insight into the structured lymphatic dissemination of sarcoidosis. Frequent FDG uptake in upper abdominal lymph nodes, particularly when accompanied by thoracic involvement, represents a characteristic finding in sarcoidosis. Recognition of this pattern can improve diagnostic accuracy and help differentiate sarcoidosis from other systemic diseases. This study assessed lymph node involvement on FDG-PET/CT in patients with suspected or known cardiac sarcoidosis, revealing distinct dissemination patterns into the upper abdomen. These findings enhance understanding of disease pathophysiology and may improve diagnostic evaluation.