Ovarian Clear Cell Adenocarcinoma With Low 68Ga-FAPI-46 and Low 18F-FDG Uptake on PET/CT

A 67-year-old woman presented with a 12 × 20 × 24-cm adnexal tumor. Ultrasonography revealed an irregular, multilocular tumor, with increased flow in the solid components, and ascites-features that are consistent with ovarian cancer. The patient underwent 18 F-FDG PET/CT and 68 Ga-FAPI-46 PET/CT, both of which showed low uptake values. Histopathology confirmed ovarian clear cell adenocarcinoma (OCCC), a less common subtype that is underrepresented in FAPI PET/CT studies so far. Low 18 F-FDG uptake is a known feature of OCCC and has been previously reported; however, this case identifies OCCC as a potential pitfall in 68 Ga-FAPI-46 PET/CT.