99mTc-FAPI-46 SPECT/CT in Ewing Sarcoma: Findings in Diverse Metastatic Presentations.

Abstract

This report evaluates 99mTc-FAPI-46 SPECT/CT in 2 young men with advanced metastatic Ewing sarcoma, demonstrating high tumor-to-background contrast and broad lesion detectability for skeletal and soft-tissue lesions. Case 1 showed widespread FAPI uptake throughout multiple osteoblastic skeletal metastases alongside avid pleural metastatic lesions. Case 2 exhibited intense FAPI avidity across several aggressive sites, including a recurrent spinal tumor, an invasive neck mass, and extensive lytic bone lesions, while demonstrating discordant thoracic uptake. Overall, FAPI-46 SPECT/CT serves as a powerful molecular imaging tool, providing excellent visualization by effectively mapping active stromal remodeling across diverse metastatic presentations.