Gastrointestinal stromal tumors are common mesenchymal tumors of the gastrointestinal tract and GISTs are mainly distributed in the stomach, small intestine, colon, and outside the gastrointestinal tract. Distribution in the small intestine accounts for approximately 20% of the total cases of GISTs. Malignant stromal tumors mainly metastasize to the liver, peritoneum, lung, bone, lymph node, and skin, and subcutaneous metastases are relatively rare. Metastases to the bone head are high-risk stromal tumors.[8–10] Gastrointestinal stromal tumors mainly occur in patients over 50 years of age, with a median age of 55–65 years old, but there is no gender preference. The incidence is 5–20% in patients younger than 40 years of age, while incidence in children is rare.  In this study, the age of the patients was in the range of 30–78 years old, with a mean of 57.60 ± 11.07 years old. There was no significant difference in gender and age between the two groups (Table 1), which is consistent with previous reports. The common clinical symptoms of SBGISTs are gastrointestinal bleeding, abdominal pain, abdominal mass, complete or incomplete intestinal obstruction, and occasional gastrointestinal perforation, and some of the clinical symptoms are not obvious, similar to the clinical symptoms of other small intestinal tumors. Moreover, there is no obvious special performance and is more prone to misdiagnosis[11, 12] There was no significant difference in gastrointestinal bleeding between the two groups (P > 0.05). According to the age and gender of patients, clinical symptoms, and risk of SBGISTs, we should be attentive for the possible diagnosis of SBGISTs when reading the film and try to reduce misdiagnosis and missed diagnosis. Eighty percent of GIST cases are associated with tyrosine kinase protein (c-KIT) mutation. Moreover, immunohistochemical analysis of GISTs usually show the expression cluster of differentiation 117 (CD117) and discovered on gastrointestinal stromal tumors protein 1 (DOG1). Positive CD117 expression can distinguish SBGISTs from small intestinal tumors.[13–15] The results for CD117, DOG1, and cluster of differentiation 34 (CD34) expression in this study were 100%, 100%, and 90.7%, respectively, which are consistent with those reported in the literature.
Univariate analysis of SBGISTs showed that there were significant differences between the low-risk and high-risk groups in terms of lesion length, boundary between the lesion and surrounding tissue, lesion lobulation, unenhanced density, ulcer, necrotic cystic degeneration, growth pattern, and lesion location (Table 2,3). Multivariate analysis identified uneven tumor unenhanced density as an independent risk factor for high-risk SBGISTs (Table 5). We believe that when the growth of tumor cells is more active, the growth rate of small blood vessels in the tumor is less than that of tumor cells, and the blood supply is insufficient, which leads to uneven density CT manifestations such as ulcers, necrotic cysts, and bleeding. It has been reported that the CT signs of gastrointestinal GISTs such as tumor edge, shape, tumor growth pattern, necrosis, and enhancement pattern are related to risk stratification[16–19]. Mazzei MA et al  show that the CT percentage of intralesional hypodensity as a CT surrogate of mitotic count demonstrates a good correlation with Miettinen risk assessment index in risk stratification of GIST patients, moreover CT percentage value of hypodensity >20% can be use as a possible accurate CT index to predict the metastatic potential of GISTs. Huh et al found that gastric GIST tumors combined with necrosis are an independent risk factor. At present, there are no consistent results regarding the risk of bleeding and calcification in SBGISTs. In our study, there was no significant difference between the two groups in bleeding and calcification, which needs to be further explored.
The results of this study showed that tumor length ≥ 4.8 cm was an independent risk factor for high-risk SBGISTs, which had high accuracy in the diagnosis of high-risk SBGISTs(Table 5). This indicated that in SBGISTs, a tumor with a maximum diameter greater than 4.8 cm can be considered high-risk SBGISTs. At present, many studies have found that tumor length ≥ 5 cm is an independent risk factor for gastrointestinal GISTs[10, 14, 18, 19, 21], which is similar to the results of this study. Our results showed that there was a significant difference in the growth pattern of tumors between the two groups, which indicated that the risk of SBGISTs in different growth patterns was different. There were no significant results from the multivariate analysis. At present, studies have found that extraluminal tumor growth is an independent risk factor for gastric GISTs. Our results showed that 38 cases of extraluminal growth were the most common in the high-risk group, and the tumors were all large. The growth pattern of tumors had reference significance for the preoperative risk grading of SBGISTs. In our study, the difference between the duodenum, jejunum, and ileum between the two groups was statistically significant. The incidence rate of SBGIST in the jejunum was higher than those of the duodenum and ileum. The results of the multivariate analysis were not statistically significant. We found that only three cases SBGIST in the ileum were found in the low-risk group, which may be related to the small sample size. We also found that lesion location was an independent risk factor for gastrointestinal GISTs. The risk of non-gastric GISTs is higher than that of gastric GISTs.[13, 14] Currently, there is limited research on the SBGIST fraction. Studies have suggested a higher incidence in the jejunum than in the ileum; however, the risk level was not analyzed.
The results of this study found that the CT values in all phases of CT enhancement, the added value of contrast-enhanced CT, and the enhancement modality differed significantly between the two groups. The ROC curve analysis of arterial phase CT values, arterial phase added values, venous phase added values, and the net value of enhancement in the venous phase showed some accuracy for the diagnosis of SBGISTs with lower risk, CT values in the arterial phase and the degree of enhancement in the arterial phase were more accurate than the other signs(Table 4). The results of the multivariate analysis suggested that the CT value in the arterial phase was an independent risk factor for the risk degree of SBGISTs, and when the CT value in the arterial phase was lower than 72.6 Hu, it was suggestive of high-risk SBGISTs. Qian su,s et al. found that the CT values in the venous and delayed phases were significantly different between the groups without risk grade SBGISTs. It was found that the blood supply of SBGISTs was abundant, and thickening of the feeding arteries could be seen in the tumor growth sites (Figure 1). The lesion was smaller, and the enhancement was more obvious in the arterial phase than that in the other phases; therefore, the higher the intensity CT value in the arterial phase, the more homogeneous the enhancement was, suggesting a lower degree of danger, as shown in (Figure 2). When the tumor was larger, its enhancement time was relatively prolonged, and the enhancement in the arterial phase was weaker, with gradually slower enhancement or progressive enhancement. The plain CT value results were not statistically different between the two groups, considering that the measured values were all taken from the solid component, so there was no differential result.
This study has some limitations. First, we did not collect cases in the intermediate-risk group. We consulted experts in the Department of Pathology of our hospital to check again. Consulting the guidelines, we found that the number of cases in the intermediate-risk group was small, and there was no evidence-based medicine. Reviewing relevant reports at home and abroad, only a few articles have mentioned cases of SBGISTs in the intermediate-risk group.[21, 24] After discussing and studying with pathology experts, we found that the clinical symptoms of SBGISTs were not typical. Most of the patients with symptoms were found to have larger lesions or higher risk, while patients with smaller lesions were found by physical examination. According to the guidelines, the lesions in the medium-risk group and the very low-risk group were small (≤ 2 cm), but the mitotic images in the medium-risk group were high, and only six cases in this group were ≤ 2 cm. Moreover, the mitotic images were low, so they were classified into the very low-risk group. The clinical symptoms of patients with small lesions are not obvious, they choose not to operate temporarily, or there is a risk of missed diagnosis due to the small lesions, so it is difficult to collect cases in the medium-risk group. Second, this was a retrospective study that used different CT models and unavoidable selection bias. Therefore, further prospective and multicenter studies with larger sample sizes are required.