Predominance and homogeneity patterns of physiological FDG accumulation in thoracic and lumbar vertebrae: suspected mechanism of "bone pseudometastasis" on FDG-PET in Japanese patients with esophageal cancer.

OBJECTIVE: False-positive bone lesions (bone pseudometastases) have been often reported in patients with esophageal cancer (EsoC). This study aimed to evaluate the vertebral 2-deoxy-2-[18F] fluoro-D-glucose (FDG) accumulation pattern in patients with newly diagnosed esophageal cancers and other malignancies (OtherT) to elucidate the possible mechanism that causes bone pseudometastasis. METHODS: FDG positron emission tomography/computed tomography performed for 90 patients with EsoC, and 112 patients with OtherT was retrospectively evaluated. The uptake pattern in the thoracic (Th) and lumbar (L) vertebrae was visually assessed regarding predominance (TL, Th ≒ L; Td, Th > L; Ld, L > Th), main intensity compared with the uptake in the blood pool (BP) (Grade 1 < BP, Grade 2 ≒ BP, or Grade 3 > BP), and homogeneity (homogeneous, heterogeneous, marginal, or spotty). The patterns between EsoC and OtherT and between Th and L were compared. RESULTS: TL, Td, and Ld patterns were observed in 51.1%, 48.9%, and 0% in EsoC and 79.7%, 20.3%, and 0% in OtherT. Though Grade 2 was most frequently observed in both groups, the ratio of Grade 3 in Th and Grade 1 in L was significantly higher in EsoC than in OtherT. Heterogeneous and spotty patterns were more frequently observed in L and in EsoC, and these were strongly associated with Td pattern. CONCLUSION: Td pattern was frequently seen, especially in EsoC, and was strongly associated with a heterogeneous or marginal pattern in the L. Heterogeneous marrow distribution with declined lumbar uptake is suspected as the mechanism of bone pseudometastasis.