MRI Features of Gastrointestinal Stromal Tumors

Objective: The purpose of this study was to investigate the MRI features of gastrointestinal stromal tumors (GISTs) with special emphasis on the dynamic enhancement pattern and findings of diffusion restriction.

Materials And Methods: Forty-two patients with pathologically proven GISTs who underwent MRI that included dynamic contrast-enhanced and diffusion-weighted imaging (DWI) were included in this study. Two abdominal radiologists analyzed the MR images in consensus regarding the morphologic features, enhancement degree and pattern, and findings of diffusion restriction. The mean apparent diffusion coefficient (ADC) values of the tumors were measured by one of the radiologists. The MRI features and mean ADC values were analyzed with respect to tumor size and malignancy risk.

Results: Small GISTs (≤ 5 cm, n = 25) appeared as round tumors with strong and homogeneous arterial enhancement and a persistent enhancement pattern. Large GISTs (> 5 cm, n = 17) appeared as lobulated tumors with mild heterogeneous gradual enhancement, and they frequently exhibited intratumoral cystic change (n = 13). The prevalence of intratumoral cystic change was higher in the moderate to high risk group than in very low to low risk group (p < 0.05). There was negative linear correlation between the mean ADC values and the malignancy risk of GISTs (r = -0.670, p < 0.05).

Conclusion: Small GISTs had MRI features different from the well-known imaging features of large GISTs. The presence of intratumoral cystic change and a low mean ADC value may be helpful for predicting the high malignancy potential of GISTs.