The usefulness of positron emission tomography-computed tomography (PET-CT) with 
A retrospective study was conducted in 2 centers and included patients who met the American College of Rheumatology/European League Against Rheumatism 2016 criteria for primary SS and had undergone PET-CT. Two independent readers who were blinded with regard to lymphoma diagnosis analyzed PET-CT scans. Abnormalities were compared between patients with and those without lymphoma.
Of the 45 patients included, 15 had lymphoma. Compared to patients without lymphoma, the mean size (P = 0.048) and maximum standardized uptake value (SUVmax) (P = 0.001) of the parotid glands were higher in patients with lymphoma. FDG uptake in the lymph nodes was observed in 53.3% of the patients with lymphoma and 43.3% of the patients without lymphoma, with no difference in the number of sites, uptake pattern, or mean SUVmax. Focal pulmonary uptake (nodules or condensations) was observed in 5 of the patients with lymphoma (33.3%) but only 1 patient without lymphoma (3.3%) (P = 0.01). Having an SUVmax in the parotid gland of ≥4.7 and/or the presence of focal pulmonary lesions was highly suggestive of lymphoma (sensitivity 80%, specificity 83.3%).
Some systemic manifestations of primary SS (lymphadenopathy, pulmonary involvement, and salivary gland involvement) can be visualized by PET-CT. Involvement of the lymph nodes and parotid glands is commonly observed with a similar frequency in SS patients with and those without lymphoma. An SUVmax in the parotid glands of ≥4.7 and/or the presence of focal lung lesions are associated with the diagnosis of lymphoma.