Background and purpose: Stromal tumor is one of the common gastrointestinal mesenchymal tumors. There is certain understanding about the typical cases. However

the diagnosis of those occurring in rare location or with rare imaging findings is often difficult. This research summarized this kind of cases

in order to increase the radiological knowledge of the disease. Methods: This study retrospectively analyzed clinical

radiological and pathological data from 550 patients who had stromal tumor confirmed by pathology in our hospital. Those with incomplete data were eliminated. Forty-nine patients were selected for further study according to the typical imaging findings. Results: Among these 49 patients

9 were pathologically confirmed to have extra-gastrointestinal stromal tumor

while 40 patients had gastrointestinal stromal tumor. Among the patients with gastrointestinal stromal tumor

22 were found in rare locations

12 in retroperitoneal space

3 in omentum majus and mesenterium

5 in esophagus

and 2 in prostate. Obvious cystic degeneration was found in 16 patients. Bulky calcification

such as flake or annulus

was found in 7 patients. The analysis result of risk-stratification showed 19 patients were confirmed as high-grade among the patients with tumors found in rare locations

15 as high grade among those with obvious cystic degeneration

and 7 as high-grade among those with extra-gastrointestinal stromal tumor. Conclusion: Rare stromal tumor often occurs in the locations

such as retroperitoneal space

omentum majus and mesenterium. Obvious cystic degeneration and bulky calcification can be seen. The risk-stratification of these patients often showed high-grade. Comprehensively analyzing its clinical features and imaging findings can help improve the diagnostic accuracy.