Nephrogenic rests mimicking Wilms' tumor on CT

Area of Science:

• Pediatric oncology
• Renal pathology
• Diagnostic imaging

Background:

• Nephrogenic rests (NR) are embryonic renal tissue remnants with malignant potential.
• Wilms' tumor (WT) is the most common pediatric renal malignancy.
• Radiologic imaging is crucial for differentiating NR from WT, with growth on serial studies being a key indicator of malignancy.

Observation:

• A 2-year-old girl with sporadic aniridia presented with two biopsy-proven NR.
• These NR exhibited imaging characteristics indistinguishable from WT.
• One NR demonstrated growth on serial imaging, mimicking malignant transformation.

Findings:

• Despite radiographic signs suggestive of WT, pathologic examination confirmed both lesions as benign hyperplastic NR.
• This case highlights the overlap in imaging features between NR and WT.
• Growth on serial imaging does not definitively confirm malignancy in NR.

Implications:

• Challenges in differentiating NR from WT based solely on imaging.
• The importance of integrating imaging findings with clinical context and pathologic confirmation.
• Potential for overdiagnosis or overtreatment of benign lesions if imaging is the sole diagnostic criterion.