Hypointense hepatocellular carcinomas on apparent diffusion coefficient mapping: Pathological features and metastatic recurrence after hepatectomy

Aim: The present study aimed to evaluate pathological features of hepatocellular carcinomas (HCC) appearing hypointense on the apparent diffusion coefficient (ADC) map, and to elucidate the association between the signal intensity on the ADC map and metastatic recurrences after hepatectomy. Methods: In total, 52 consecutive patients with initial hypervascular HCC (solitary lesion <= 5 cm in diameter) without vascular invasion on imaging were examined by diffusion-weighted magnetic resonance imaging before hepatectomy. The signal intensities of HCC on the ADC map were visually compared with the surrounding liver and categorized as hypointense or non-hypointense. Intrahepatic metastatic recurrence was defined as more than three intrahepatic recurrences. Results: The 52 HCC were evaluated as 26 hypointense and 26 non-hypointense tumors. No significant differences between the hypointense and non-hypointense groups were seen for age, sex, etiology, tumor size and tumor marker levels. However, in resected specimens, significant differences between the two groups were noted for histological grade and microscopic portal invasion. The percentages of poorly differentiated HCC and microscopic portal invasion in the hypointense group were significantly higher than those in the non-hypointense group. The cumulative 3-year metastatic recurrence rates of the hypointense and non-hypointense groups on the ADC map were 56% and 13% (P = 0.001), respectively. Multivariate analyses indicated that hypointensity on the ADC map was the only independent factor related to metastatic recurrence. Conclusion: Hypointense HCC on ADC mapping are characterized by poor histological differentiation and more frequent microscopic portal invasion, and are significantly associated with metastatic recurrences after hepatectomy.