Hypoxia is important in F‑18 FDG accumulation in thecoma‑fibroma tumors on F‑18 FDG PET/CT scans.

Several studies have noted benign thecoma‑fibroma tumors with positive F‑18 fluorodeoxyglucose (FDG) accumulation mimicking malignant ovarian tumors following F‑18 FDG positron emission tomography (PET). The present study analyzed four cases with false‑positive F‑18 FDG PET/computed tomography (CT) diagnoses of thecoma‑fibroma tumors as malignant tumors due to F‑18 FDG accumulation, compared with eight cases of FDG‑positive ovarian cancers and two cases of FDG‑negative fibromas. Hypoxia inducible factor (HIF)‑1α expression was examined in the six thecoma‑fibroma tumors using reverse transcription‑polymerase chain reaction (RT‑PCR). The four F‑18 FDG‑positive cases exhibited higher cellularity, maximum standard uptake and signal intensity on T2‑weighted imaging, and gadolinium (Gd) enhancement using magnetic resonance imaging than the two FDG-negative fibroma cases. In the F‑18 FDG‑positive thecoma‑fibroma group, Ki‑67 expression was low and LAT1 expression was not identified, ruling out the diagnosis and potential for malignancy. However, considerable glucose transporter 1, HIF‑1α, and vascular endothelial growth factor expression was observed. HIF‑1α expression was elevated in all four false‑positive cases by RT‑PCR. From these results, it was hypothesized that hypoxia due to elevated cellularity may stimulate HIF‑1α expression and be associated with F‑18 FDG accumulation in F‑18‑positive thecoma‑fibroma tumors.