Abstract:Background and Aims Solitary fibrous tumor (SFT) is a rare subtype of soft tissue sarcoma in clinical practice. Previous studies reported that SFT occurs predominantly in the pleura, but recent studies demonstrated that it can also develop in many parts of the body. Because the occurrence rate of SFT in the retroperitoneal space is low, so there is still a lack of in-depth research on the clinical diagnosis and treatment of retroperitoneal SFT at present. Therefore, this study was performed to investigate the clinical features, diagnosis and treatment as well as the prognosis of retroperitoneal SFT through reviewing the data of 7 patients with this condition, so as to help facilitate further understanding and more attention.Methods The clinical and pathological data of 7 patients diagnosed with retroperitoneal SFT by pathological and immunohistochemical analysis after surgery or puncture biopsy in the First Affiliated Hospital of Xi'an Jiaotong University from March 2014 to September 2021 were retrospectively analyzed. The diagnosis, treatment and prognosis of the patients to summarized and analyzed.Results Among the 7 patients, 4 cases were males and 3 cases were females, with an average age of (53.3±13.2) years. The clinical symptoms were not specific, one of them had no obvious symptoms, while the other 6 cases showed varying degrees of symptoms due to tumor compression of the surrounding tissues and organs. The most common symptoms were bloating and abdominal pain. CTA examination was performed in 5 patients before operation. Among them, the tumor-feeding arteries arose from the branch of the internal iliac artery in two cases, from the internal iliac artery and the lumbar artery in one case, from the distal branch of the inferior mesenteric artery in one case, and from the splenic artery in one case, respectively. Six patients underwent radical surgical resection, of whom three cases underwent preoperative embolization and three cases underwent combined organ resection. The average operative time was (372.5±91.3) min, the average blood loss was (1 200.0±1 031.5) mL, and the average length of hospital stay was (25.7±9.3) d. For patients with and without preoperative embolization, the average length of hospital stay was (10.3±4.2) d and (11.7±2.3) d, the average drainage volume on the first postoperative day was (283.3±119.3) mL and (385.0±262.5) mL, respectively. Postoperative pulmonary infection and encapsulated retroperitoneal collections occurred in one case each among the patients without embolization. Tumor size ranged from 9 cm ×7 cm×6 cm to 25 cm×20 cm×10 cm. Microscopic examination of the tumor showed that there were spindle-shaped cells of uneven distribution with varying degrees of atypia, occasional findings of thin-walled "staghorn" vasculature, and frequent presence of collagen fibers in the interstitium. The positive rates of immunohistochemical staining for CD34 and Ki-67 were 100% (7/7), CD99 and vimentin were 100% (6/6), STAT6 was 100% (5/5), and Bcl-2 was 50% (3/6), and S-100 was 14% (1/7), respectively. During the follow-up period for 2-66 months, one case was lost to follow-up and no recurrence or metastasis was found in the other cases.Conclusion Retroperitoneal SFT has no specific clinical manifestations. Imaging examinations have guiding significance for preoperative evaluation and surgical planning, and the final diagnosis depends on the results of pathological examination and immunohistochemical analysis. Radical surgical resection is the main treatment method. Preoperative embolization has positive effect on shortening the postoperative hospital stay, reducing postoperative drainage volume and the occurrence of complications. Long-term follow-up guided by risk stratification is of great importance.