To explore the imaging findings and pathological features of solitary fibroma tumor in the abdomen and pelvis.

The imaging findings of 7 cases pathologically confirmed solitary fibroma tumor(SFT)in the abdomen and pelvis were retrospectively reviewed from March 2015 to March 2021 in Northern Jiangsu People′s Hospital, and compared with the pathological features.

Among the 7 SFT patients, there were 6 males and 1 female, with an average age of 57(27-71)years.One patient received only PLAIN CT scan of abdomen, and 6 patients received plain CT or MRI scan or enhanced CT scan.The tumor was located in pancreas(n=1), abdominal cavity(n=2), pelvic cavity(n=4). Only 1 case had multiple lesions, and the rest were single lesion.The average maximum diameter of the lesions was 90 mm.In plain CT, lesions showed iso-density or slightly low-density shadow with uniform or uneven density, and 2 cases with small cystic and 1 case with calcification.In enhanced images, only 1 case showed uniform slight enhancement, 5 cases showed enhanced vascular shadow in arterial phase, and 4 cases showed " map" enhancement in parenchymal phase.MRI showed slightly low signal intensity on T1WI, equal or slightly higher or slightly lower mixed signal intensity on T2WI, and empty signal intensity on T2WI was observed in 1 lesion, which showed delayed enhancement on enhanced scanning.Postoperative metastasis occurred in 2 of 7 cases, and adjacent bone invasion occurred in 1 case.Histologically, SFT was mainly composed of spindle cells and collagen fibers.Immunohistochemistry showed high expression of CD34 and low expression of Ki-67, while malignant SFT showed reduced expression of CD34 and high expression of Ki-67.

Abdominal and pelvic SFT is relatively rare, and its imaging manifestations have certain specificity, and can reflect its pathological features, which is helpful for the diagnosis and differential diagnosis of the disease.