Usefulness of 18 F-FDG Positron Emission Tomography (PET) for the diagnosis of lymphoma in primary Sjögren's syndrome.

OBJECTIVES: Positron emission tomography with computed tomography (PET-CT) with 18 F-FDG may be useful in patients with primary Sjögren's syndrome (pSS), but its usefulness for the diagnosis of lymphoma is unclear since it may reveal abnormalities due to systemic manifestations. We aimed to compare 18 F-FDG PET-CT between pSS patients with or without lymphoma, to identify patterns associated with lymphoma.

METHODS: Retrospective study conducted in 2 centers including pSS patients (ACR/EULAR 2016 criteria) who undergone PET-CT. Two independent readers analyzed PET-CT blinded to lymphoma diagnosis. Abnormalities were compared between patients with and without lymphoma.

RESULTS: Among the 45 patients included, 15 had lymphoma. Compared to non-lymphoma patients, mean size (p=0.048) and maximum standardized uptake value (SUVmax) of the parotid glands (p=0.001) were higher in lymphoma patients. Lymph node FDG uptake was observed in 53.3% of patients with lymphoma and 43.3% without lymphoma, with no difference in number, repartition or mean SUVmax. Focal pulmonary uptake (nodules or condensations) was observed in 5 (33.3%) patients with lymphoma but only one (3.3%) patient without lymphoma (p=0.01). Having a SUVmax of parotid gland ≥ 4.7 and/or the presence of focal pulmonary lesions was highly suggestive of lymphoma (sensitivity = 80%, specificity = 83.3%).

CONCLUSION: Some systemic manifestations of pSS (pulmonary, lymphadenopathies and salivary gland involvements) can be visualized by PET-CT. Lymph nodes and parotid glands involvements are commonly observed with a similar frequency in patients with and without lymphoma. Nevertheless, SUV max of parotid glands ≥ 4.7 and/or focal lung lesions were associated with lymphoma diagnosis. This article is protected by copyright. All rights reserved.