Solid splenic masses:: Evaluation with 18F-FDG PET/CT

Our objective was to assess the role of F-18-FDG PET/CT in the evaluation of solid splenic masses in patients with a known malignancy and in incidentally found lesions in patients without known malignancy. Methods: Two groups of patients were assessed: (a) 68 patients with known malignancy and a focal lesion on PET or a solid mass on CT portions of the PET/CT study; and (b) 20 patients with solid splenic masses on conventional imaging without known malignancy. The standard of reference was histology (n = 16) or imaging and clinical follow-up (n = 72). The lesion size, the presence of a single versus multiple splenic lesions, and the intensity of 18F-FDG uptake expressed as a standardized uptake value (SUV) were recorded. The ratio of the SUV in the splenic lesion to the background normal splenic uptake was also calculated. These parameters were compared between benign and malignant lesions within each of the 2 groups of patients and between the 2 groups. Results: The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of F-18-FDG PET/CT in differentiating benign from malignant solid splenic lesions in patients with and without malignant disease were 100%, 100%, 100%, and 100% versus 100%, 83%, 80%, and 100%, respectively. In patients with known malignant disease, an SUV threshold of 2.3 correctly differentiated benign from malignant lesions with the sensitivity, specificity, PPV, and NPV of 100%, 100%, 100%, and 100%, respectively. In patients without known malignant disease, false-positive results were due to granulomatous diseases (n - 2). Conclusion: F-18-FDG PET can reliably discriminate between benign and malignant solid splenic masses in patients with known F-18-FDG-avid malignancy. It also appears to have a high NPV in patients with solid splenic masses, without known malignant disease. F-18-FDG-avid splenic masses in patients without a known malignancy should be further evaluated as, in our series, 80% of them were malignant.