Background and purpose: Solid pseudopapillary tumor of the pancreas (SPTP) is rare

and there are some differences between benign and malignant SPTP not only in clinical treatment but also in future prognosis. The purpose of this study was to investigate the characteristics of benign and malignant SPTP and differential diagnosis on computed tomography scan

in order to improve the accuracy of preoperative diagnosis. Methods: A total of 69 SPTP patients cofirmed by pathology were included. Each patient was diagnosed through the clinical and CT features by 3 radiologists. Results: Thirteen (18.84%) patients (9 females and 4 males) were confirmed as malignant SPTP. The tumors in 56 (81.16%) patients (45 females and 11 males) were diagnosed as benign SPTP. There was no significant difference in gender (P=0.458) between the groups. The mean age of malignant SPTP patients was significantly higher than that of benign SPTP patients ［39 (16-56) years vs 31 (14-56) years

P=0.001］. The mean tumor size was 6.2(2.2-12.0)cm in malignant group and 5.5(1.2-13.0) cm in benign group

respectively. The size of tumor was equal or larger than 5.0 cm in 31 patients (benign vs malignant 21∶10

P=0.014). Twenty-eight lesions showed incomplete fibrous pseudocapsule (benign vs malignant 19∶9

P=0.028). There were no significant differences in lesion location

morphology

proportion of cystic or solid component between malignant and benign groups (P0.05). Conclusion: Malignant SPTP patients were significantly older than benign SPTP patients. The large tumor size (≥5 cm) and incomplete fibrous pseudocapsule may suggest malignancy of SPTP.