Gastrointestinal Stromal Tumors:radiologic Features With Pathologic Risk Grade Correlation

Objective: The aim of this study was to identify some predictors of different risk grade of GISTs on MSCT and MRI imagings.Materials and Methods: Between September 2007 and December 2014, 191 GISTs patients were retrospectively reviewed who underwent CT and MRI scan. All patients underwent surgical resection and patients with GISTs confirmed by post-operative pathology and immunohistochemistry. We defined tumors as very low, low, middle and high risk grade. Becance very low risk grade tumors were limited, we regard very low and low risk grade as one group.(1) CT date: Between June 2011 and December 2014, 148(65, male; 83, female) GISTs patients were retrospectively reviewed. The mean age of the patients was 59 years(range, 32-82 years). Patients received unenhanced and enhanced scan of 2 MSCT(16-slices, 64-slices). CT images were transported to PACS(picture archiving and communications system) for muti-plannar reconstruction(MPR) review. We analyzed CT features including: tumor site, size, shape, boundary, growth pattern, enhancement pattern, enhancement degree, cystic-necrotic, ulceration, calcification, metastasis and ascites. The CT features were compared with tumor risk grade.(2) MRI date: Between September 2007 and December 2014, 43(20, male; 23, female) GISTs patients were retrospectively reviewed. The mean age of the patients was 57 years(range, 30-78 years). Patients received unenhanced and enhanced scan of 1.5T MRI. All patients underwent surgical resection and patients with GISTs confirmed by post-operative pathology and immunohistochemistry. We analyzed MRI features including: minimum ADC values, average ADC values, TIWI and T2 WI signal intensity, and enhancement pattern. The MRI findings were compared with the tumor risk grade.Results:(1) CT date: Among 148 tumors, 112 tumors originating from stomach, 33 tumors originating from small bowel, and 3 tumors originating from rectum. Low risk grade tumors ranged from 0.8 cm to 5.0 cm, average 2.3 ± 0.9 cm; middle risk grade tumors ranged from 2.5 cm to 10.0 cm, average 5.2 ± 1.9 cm; high risk grade tumors ranged from 2.8 cm to 25.0 cm, average 10.3 ± 4.8 cm; 77 showed regular shape, 71 showed irregular shape; 100 showed clear boundary; 48 tumors showed intraluminagrowth pattern, 55 tumors showed intra-extraluminal growth pattern, and 45 tumors showed extraluminal growth pattern. The majority tumors showed moderate or marked enhancement; 91 tumors showed heterogeneous enhancement. 74 tumors contained cystic-necrotic; 37 tumors showed ulceration. Calcification, metastasis and ascites were infrequently seen. According to CT features of different risk grade, statistical analysis showed that tumors originating from small bowel and showed larger size, irregular shape, unclear boundary, intra-extraluminal or extraluminal growth pattern, heterogeneous enhancement, cystic-necrotic, metastasis and ascites showed more malignancy behavior(P < 0.05). Tumors enhancement degree and calcification had no correlation with tumor risk grade(P > 0.05).(2) MRI date: 43 tumors showed high signal intensity on DWI imagines. Statistical analysis showed that average ADC values and signal intensity had correlation with tumor risk grade(P < 0.05). Lower average ADC values and heterogeneous signal intensity are suggestive of higher aggressive risk. Statistical analysis showed that minimal average ADC values and enhancement pattern had no correlation with tumor risk grade(P > 0.05).Conclusion:(1) Low risk grade tumors were more often originating from stomach and showed small size, regular shape, clear boundary, intraluminal or extraluminal growth pattern, homogeneous enhancement. The tumors were uncommon seen of the ulceration, cystic-necrotic, metastasis and ascites.(2) Middle risk grade tumors’ s radiologic features were between low and high risk grade.(3) High risk grade tumors were more often originating from small bowel and showed larger size, irregular shape, unclear boundary, intra-extraluminal or extraluminal growth pattern, heterogeneous enhancement, ulceration, cystic-necrotic, metastasis and ascites.(4) CT examination has high spatial resolution and it’s sensitive to the calcifation and tumor’s growth pattern. But it’s difficult to diagnose of the ulceration and the cystic-necrotic. MRI is sensitive to the cystic-necrotic. But the machine need much more time and the images were easy affected by the motion. Thus MRI has certain limitation.