Abstract: 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.

Key words: Stromal tumor, CT, MRI