Incidental focal 18F-FDG uptake in frontal process of maxilla on PET/CT: Incidence and clinical significance

1533 Objectives We investigated the incidence, image findings, and clinical significance of incidental focal 18F-FDG uptake in frontal process of maxilla on PET/CT. Methods Subjects were 41,528 consecutive PET/CT scans, which were retrospectively reviewed to find incidental focal uptake in frontal process of maxilla. When a focal uptake was observed, SUVmax, size in maximal diameter, and feature on CT of that lesion were evaluated. Clinical significance of that lesion was evaluated by clinical follow-up (F/U), F/U PET/CT, and F/U CT. Results Forty patients (0.11%; M : F = 28:12; age 59 ± 12 y; 39 patients for cancer work-up, 1 for cancer screening) had an incidental focal uptake (Lt : Rt = 14 : 26). SUVmax was 3.5 ± 1.0. On the CT images of PET/CT, all lesions showed ground glass attenuation with or without bony expansion like fibrous dysplasia (FD), and maximal diameter was 6.2 ± 2.0 mm. In 16 patients where F/U PET/CT was available, there was no significant difference in SUVmax and size of those lesions between the scans (3.1 ± 0.9 vs. 2.2 ± 0.7; 5.3 ± 1.4 mm vs. 5.2 ± 1.3 mm). In 6 patients where F/U CT was available, there was no significant difference in size of those lesions between the scans (6.2 ± 2.8 mm vs. 5.9 ± 2.2 mm). In 7 patients showing focal uptake in the maxilla, there was no significant focal uptake in that lesion on previous PET/CT, but similar FD-like appearance was shown on CT of PET/CT images. In 37 patients where clinical F/U was done (≥ 6 mo), there was no patient who had symptoms or signs related to the maxilla lesion. Conclusions Focal uptake in frontal process of maxilla is a rare incidental and persistent PET/CT finding, which can be misdiagnosed as metastasis due to high uptake. FD-like appearance on CT and the results of clinical and imaging F/U suggest that focal uptake can be interpreted as benign. However, further prospective study with a larger size of subjects is warranted.