Benign Bone Lesions Masquerading as Metastases on PET/CT Reveal Critical Diagnostic Pitfall in Pediatric Ewing Sarcoma

In a compelling new report, Dr. Emine Göknur Işık and her colleagues at Istanbul University shine a light on a rare but significant imaging pitfall: non-ossifying fibromas (NOFs) that exhibit high FDG uptake and can be mistaken for skeletal metastases in children with Ewing sarcoma.

During routine staging with F-18 FDG PET/CT in a 15-year-old boy diagnosed with thoracic wall Ewing sarcoma, the team—comprising nuclear medicine specialists Dr. Işık and Begüm Arça, radiologist Dr. Zuhal Bayramoğlu, and pediatric oncologist Dr. Ülkü Miray Yıldırım—noted two unexpected hypermetabolic bone lesions. One lesion, located in the distal right femur, demonstrated an extraordinarily high SUVmax of 19.9—surpassing even the primary tumor’s uptake of 6.7—while the second lesion in the proximal left tibia registered an SUVmax of 6.8.

Alarmed by these findings, the researchers immediately pursued targeted radiographs and MRI at the Istanbul Faculty of Medicine’s Departments of Nuclear Medicine and Radiology. Both modalities revealed well-circumscribed, cortically based lesions with classic imaging features of benign non-ossifying fibromas rather than malignancy. This crucial correlation spared the patient from unnecessary biopsy or overtreatment.

“This case emphasizes that intense FDG uptake alone is not definitive for malignancy,” notes Dr. Işık. “In pediatric oncology, where treatment decisions carry lifelong consequences, confirming benign etiologies with conventional imaging is essential to avoid overstaging and undue interventions.”

Key takeaways from this report include:

• High FDG Uptake Can Mislead: Non-ossifying fibromas may demonstrate SUVmax values that rival or exceed those of known malignant lesions.
• Multimodal Confirmation Is Vital: Radiographs and MRI remain indispensable tools for characterizing bone lesions appearing FDG-avid on PET/CT.
• Clinical Management Impact: Recognizing this pitfall protects young patients from unnecessary invasive procedures and guides appropriate, less aggressive care.

How to Cite
Işık EG, Arça B, Bayramoğlu Z, Yıldırım ÜM. FDG-Avid Non-Ossifying Fibromas Mimicking Metastases in Pediatric Ewing Sarcoma: A Diagnostic Pitfall on PET/CT. TheJODTi. 2025;1(3):5–7.