Clinical Utility of 18F-FDG PET/CT for Staging and Restaging of Pediatric Malignant Melanoma: A Single-Center Retrospective Study

Background/Objectives: Malignant melanoma is a rare entity in the pediatric population, accounting for approximately 1–3% of all childhood malignancies. Despite its rarity, it is the most common skin cancer in children. Accurate staging and monitoring are essential for treatment planning and prognosis. This study aimed to evaluate the clinical value of 18F-FDG PET/CT in staging and restaging of pediatric malignant melanoma. Methods: We retrospectively analyzed pediatric patients aged 18 years or younger who underwent 18F-FDG PET/CT imaging between 2010 and 2025 with histopathologically confirmed malignant melanoma. Demographic data, primary lesion localization, PET/CT findings, pathology reports, and clinical outcomes were recorded. Lesions were categorized as positive and negative in the final analysis. Diagnostic performance parameters (with 95% confidence intervals (CIs)) were calculated using histopathological confirmation or clinical follow-up as the reference standard, and categorical associations were assessed using Fisher’s exact test. Results: A total of 20 patients (12 females, 8 males; mean age: 11 years, range: 4–18) and 31 PET/CT examinations were included, with a mean follow-up duration of approximately 98 months. PET/CT was performed for initial staging in 17 examinations and for restaging in 14. On an examination-based analysis, PET/CT findings were negative in 22/31 (71.0%) and positive in 9/31 (29.0%) examinations. On a patient-based analysis, 12/20 (60%) patients had all examinations classified as true negative and remained disease-free throughout follow-up. 18F-FDG PET/CT demonstrated a sensitivity of 80.0% (95% CI: 49.0–94.3%), specificity of 95.2% (95% CI: 77.3–99.2%), positive predictive value of 88.9% (95% CI: 56.5–98.0%), negative predictive value of 90.9% (95% CI: 72.2–97.5%), and overall accuracy of 90.3% (95% CI: 75.1–96.7%) for the detection of clinically active disease. Agreement between PET/CT findings and clinical outcomes was substantial (Cohen’s κ = 0.77). Among the nine PET-negative restaging examinations, one was subsequently confirmed as false-negative; the remaining eight showed no evidence of active disease during the available follow-up period. Conclusions: In this exploratory retrospective study, 18F-FDG PET/CT demonstrated promising diagnostic performance for staging and restaging of pediatric malignant melanoma, with high specificity and negative predictive value. These findings should be interpreted with caution given the small sample size and retrospective design but suggest a potentially meaningful role for 18F-FDG PET/CT in the multidisciplinary management of this rare pediatric malignancy.