Diffusion-weighted magnetic resonance imaging predicts malignant potential in small hepatocellular carcinoma

Abstract Background Poor differentiation and microvascular invasion are indicators of poor outcome after hepatectomy for patients with small hepatocellular carcinoma (HCC). Aims We investigated whether gadoxetic acid-enhanced and diffusion-weighted magnetic resonance imaging (MRI) could predict these factors before hepatectomy. Methods Between July 2008 and April 2012, 75 patients who underwent hepatectomy for small HCCs (diameter: ≤3 cm, tumor number: ≤3) were consecutively enrolled. In gadoxetic acid-enhanced MRI, the signal intensity in the tumor was corrected to that in the paraspinous muscles, and the relative enhancement was calculated. In diffusion-weighted imaging, we measured the apparent diffusion coefficient (ADC). We then investigated the correlations between relative enhancement or ADC and histological grade, microvascular invasion and recurrence-free survival. Results Poorly differentiated HCCs showed significantly lower ADC than well-differentiated and moderately differentiated HCCs. There was no significant difference in the hepatobiliary phase. Only ADC was an independent predictor of microvascular invasion, and the best cut-off point of its prediction was 1.175 × 10 −3  mm 2 /s. Additionally, the recurrence-free survival was significantly shorter in low-ADC group than in high-ADC group. Conclusion ADC is useful for predicting poorly differentiated HCCs and microvascular invasion, and low ADC is associated with increased recurrence risk for small HCCs after hepatectomy.