Preserving Fertility, Not Metastases: A Pediatric FDG PET/CT Diagnostic Challenge

Area of Science:

• Nuclear Medicine
• Pediatric Oncology
• Radiology

Background:

• Ewing sarcoma is a rare bone cancer affecting children and young adults.
• Positron Emission Tomography/Computed Tomography (PET/CT) with F-18 fluorodeoxyglucose (FDG) is crucial for assessing treatment response.
• Laparoscopic testicular transposition is a prophylactic measure before pelvic radiotherapy to preserve gonadal function.

Purpose of the Study:

• To report a unique finding on F-18 FDG PET/CT in a pediatric patient with sacral Ewing sarcoma.
• To highlight the importance of recognizing physiological FDG uptake in transposed testes.
• To provide image-based documentation of this rare clinical scenario.

Main Methods:

• A 12-year-old male with sacral Ewing sarcoma underwent F-18 FDG PET/CT for treatment response assessment post-chemotherapy.
• Incidental findings on follow-up PET/CT were analyzed.
• The case involved distinguishing physiological uptake in transposed testes from potential pathological uptake.

Main Results:

• Initial F-18 FDG PET/CT showed a metabolically active lesion in the sacrum (S2-S4 vertebrae).
• Post-chemotherapy imaging demonstrated marked resolution of the lesion's uptake.
• Follow-up PET/CT incidentally revealed bilateral testes in the anterior abdominal wall, consistent with prophylactic laparoscopic testicular transposition.

Conclusions:

• F-18 FDG PET/CT is effective in assessing Ewing sarcoma treatment response.
• Nuclear medicine physicians must be aware of transposed testes and differentiate their physiological FDG uptake from pathological findings.
• This case represents the first PET/CT image-based documentation of transposed testes in this clinical context.