Metastasis Workup for Alveolar Paratesticular Rhabdomyosarcoma: 18 F-FDG PET/CT Versus 99m Tc-FAPI-46 SPECT/CT.

Abstract

We present a 19-year-old man with alveolar paratesticular rhabdomyosarcoma (RMS) who underwent restaging with both 18 F-fluorodeoxyglucose (FDG) positron-emission tomography (PET)/ computed tomography (CT) and 99m Tc-fibroblast activation protein inhibitor (FAPI)-46 single-photon emission computed tomography (SPECT)/CT after the initial surgery. Despite normal retroperitoneal lymph nodes on CT, 18 F-FDG PET/CT revealed a recurrent mass in the spermatic cord stump and an inguinal lymph node, which was not detected by 99m Tc-FAPI SPECT/CT. Our case highlights the superior efficacy of 18 F-FDG PET/CT compared with 99m Tc-FAPI SPECT/CT in restaging paratesticular RMS, consistent with previous studies demonstrating the utility of 18 F-FDG PET/CT in the initial staging of RMS. This report underscores the importance of selecting the optimal imaging modality for accurate disease assessment and management in this aggressive and rare tumor subtype.