F-Fluorodeoxyglucose positron emission tomography/computed tomography in distinguishing pediatric clear cell sarcoma of the kidney from Wilms' tumor.

Background: Clear cell sarcoma of the kidney is a rare primary renal malignancy in children and its differentiation from other renal tumors, particularly Wilms' tumor, poses significant diagnostic challenges. Notably, clear cell sarcoma of the kidney is associated with a poorer prognosis than Wilms' tumor, making the preoperative presumptive diagnosis critical for optimizing surgical resection and appropriate chemotherapy regimens.

Objective: We conducted a feasibility study to evaluate the diagnostic utility of F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) in distinguishing clear cell sarcoma of the kidney from Wilms' tumor.

Materials And Methods: This study included 19 patients diagnosed with clear cell sarcoma of the kidney and 84 patients with Wilms' tumor. Among these, 11/19 patients with clear cell sarcoma of the kidney and 28/84 patients of Wilms' tumor displayed positive findings on F-FDG PET/CT imaging, which were subsequently validated as tumor lesions by histologic examination, conventional imaging, or clinical follow-up. A retrospective analysis of the imaging features of clear cell sarcoma of the kidney and Wilms' tumor lesions on F-FDG PET/CT scans was conducted. Receiver operating characteristic (ROC) curve analyses were performed to determine the optimal cutoff of the maximum standardized uptake value (SUVmax) for diagnostic prediction.

Results: The mean SUVmax for all lesions of clear cell sarcoma of the kidney was significantly lower than that of Wilms' tumors (3.9 vs. 7.4; P<0.001). When analyzed separately, primary lesions (3.6 vs. 6.6; P=0.042) and metastatic lesions (4.0 vs. 7.8; P=0.011) both had lower SUVmax in clear cell sarcomas of the kidney compared with Wilms' tumors. ROC curve analysis revealed a cutoff SUVmax of 4.3, which effectively supported the diagnosis of clear cell sarcoma of the kidney over Wilms' tumor, with a sensitivity of 75.0% and a specificity of 87.5%.

Conclusions: Clear cell sarcomas of the kidney exhibited a significantly lower SUVmax on F-FDG PET/CT when compared to Wilms' tumor lesions, with a proposed threshold SUVmax of 4.3 serving as an effective criterion for differentiation. Consequently, F-FDG PET/CT demonstrated potential in distinguishing clear cell sarcoma of the kidney from Wilms' tumor in cases involving large renal masses.