Tumors in pediatric patients at diffusion-weighted MR imaging: apparent diffusion coefficient and tumor cellularity

Area of Science:

• Pediatric Radiology
• Oncology
• Diffusion-Weighted Magnetic Resonance Imaging

Background:

• Extracranial mass lesions in children require accurate diagnosis.
• Apparent diffusion coefficient (ADC) derived from diffusion-weighted MRI is a potential imaging biomarker.
• Histopathologic cell count is a key factor in tumor characterization.

Purpose of the Study:

• To investigate the relationship between ADC and histopathologic cell count in pediatric extracranial mass lesions.
• To determine if ADC can differentiate between benign and malignant extracranial masses in children.

Main Methods:

• Prospective study of 19 children with extracranial mass lesions.
• Magnetic resonance imaging (MRI) including diffusion-weighted sequences was performed.
• ADC values were compared with histopathologic cell counts; statistical analysis included inverse regression and Mann-Whitney U test.

Main Results:

• An inverse relationship was observed between ADC and cell count (R(2) = 0.541, P < .001).
• Median ADC for benign lesions was 1.35 x 10(-3) mm(2)/sec (SD, 0.68); for malignant lesions, it was 1.00 x 10(-3) mm(2)/sec (SD, 0.29).
• No significant difference in ADC was found between benign and malignant lesions (P = .069).

Conclusions:

• Cellularity is significantly related to ADC, but not the sole determinant.
• ADC is not a reliable tool for differentiating benign from malignant extracranial mass lesions in children.