[18F]FAPI-74 PET for Preoperative Assessment of Peritoneal Dissemination in Ovarian Cancer: A Case Series with Surgical and Histopathological Correlation

Background/Objectives: Accurate preoperative assessment of peritoneal dissemination is essential in ovarian cancer because it influences surgical strategy and the achievement of complete gross resection. However, [18F]FDG-PET may be limited in detecting lesions with low glycolytic activity and in differentiating malignancy from inflammatory changes. This case series evaluated the clinical relevance of [18F]FAPI-74 PET/CT for preoperative assessment of peritoneal dissemination in ovarian cancer. Methods: Four patients underwent [18F]FAPI-74 PET/CT as part of preoperative evaluation, with comparison to [18F]FDG-PET/CT when available. Imaging findings were correlated with intraoperative observations and histopathological results, including immunohistochemical assessment of fibroblast activation protein and α-smooth muscle actin. Results: FAPI-PET detected peritoneal dissemination not identified by FDG-PET in several cases, including occult metastasis confirmed histologically and additional lesions after neoadjuvant chemotherapy. FAPI-avid lesions showed stromal activation on immunohistochemistry, supporting the biological basis of FAPI uptake. In one case, additional FAPI uptake may have been partly influenced by inflammatory changes associated with bloody ascites. Conclusions: FAPI-PET may provide complementary information by visualizing stromal components of ovarian cancer and may support preoperative mapping of peritoneal dissemination, although interpretation should consider inflammatory conditions.