Heterotopic Pancreas Masquerading as Omental Nodule on FAPI PET/CT.

Chylous ascites, attributed to various etiologies including malignancy, tuberculosis, ruptured lymphatics, and congenital lymphatic disorders, manifests as abdominal distension. Our patient presented with this condition, and an elevated CA 125 prompted further investigation. Flourine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET-CT) revealed a metabolically inactive omental nodule, while gallium 68 fibroblast activation protein inhibitor (Ga-68-FAPI) PET-CT demonstrated uptake in the same nodule and low-grade uptake in bilateral adnexae. Colloid liver scan ruled out chronic liver disease. Surprisingly, lymphoscintigraphy showed no lymphatic leak. Histological examination of the omental nodule confirmed heterotopic pancreas (HP) in the small bowel mesentery, with normal adnexae. This case report illuminates the diagnostic challenges entailed in HP and signifies a pioneering instance in the literature where evidence of HP was identified for the first time on Ga-68-FAPI PET-CT during the investigative process.