Unveiling Ovarian Cancer With [ 18 F]FDG and [ 68 Ga]Ga-FAPI-46 PET/CT : A Rare Case of Malignant Pericardial Effusion.

A 71-year-old woman presented with fatigue, dyspnea, and weight gain, suggestive of a serious systemic disease. CT revealed a large pericardial effusion, and subsequent [ 18 F]FDG PET/CT showed focal areas of elevated FDG uptake in the pericardium and moderate, symmetric FDG uptake in normal-sized ovaries. Pericardial effusion cytology indicated a gynecological malignancy. Additional [ 68 Ga]Ga-FAPI-46 PET/CT demonstrated more distinct uptake in the pericardium and lymph nodes. Histopathology of ovarian surgical specimens confirmed poorly differentiated ovarian cancer. This case highlights the utility of FDG PET/CT in evaluating pericardial effusion of unknown etiology and introduces the potential role of FAPI PET/CT in such scenarios.