Abstract： Objective To explore the correlation between pathologic findings of pancreatic ductal adenocarcinoma accompanied with cystic lesion and their radiological images .Methods The pathological and radiological data of 97 cases with cystic lesion of 560 patients who were diagnosed as pancreatic ductal adenocarcinoma based on postoperative pathology were retrospectively analyzed .All the patients underwent CT and MRI examinations .Results Postoperative pathological report showed that solid masses and cysts coexisted in all the lesions .Solid masses had compact structures and consisted of innumerable fibrous collagen mixed with tumorous tubular or acinar gland tissue but lack of vessels and inflammatory cells were infiltrated in tissues surrounding the tumors .As for the accompanied cystic lesions , 54 cases ( 56%) were pseudocysts , 22 cases (23%) were retention cysts, 12 cases (12%) were pancreatic intraductal papillary mucinous neoplasms ( IPMN) , and 9 cases (9%) were the necrosis and cystic changes of the tumors .Solid masses were hypodense or iso-hypodense in CT, and hypodense on T1 WI and isodense or iso-hyperdense on T2 WI in MR.The focal calcification was detected in only one mass .Seventy-eight cases displayed slight enhancement and 19 cases displayed no enhancement after enhancement .The tumor′s boundary were unclear in all cases .The cystic lesions which were located in masses were only observed in patients with tumors′necrosis and cystic degeneration, and other cystic lesions were adjacent to the solid masses .Single cyst was found in 70 cases (49 with pseudocysts , 12 with retention cysts , 9 tumors′necrosis and cystic degeneration ,) and multiple cysts were in 27 cases (5 with pseudocysts, 10 with retention cysts ,12 with IPMN).Exudation appeared surrounding the tumors in all cases accompanied with pseudocysts , and the cystic wall was attached to the spleen in 10 cases and the kidney in 5 cases.Hemorrhage appeared in 16 cases with pseudocysts .Pancreatic ducts were blocked by tumor masses and the proximal duct was dilated in 80 cases.Common bile ducts were obstructed with the proximal duct dilated in 18 patients.Splenic veins were infiltrated in 11 cases.Wall nodular lesions were seen in 5 cases with cystic degeneration .Conclusions Pancreatic ductal adenocarcinoma is a highly invasive tumor with compact structures , and the tumors′cystic degeneration is uncommon in such patients .Most of the cystic lesions accompanied with the tumors are pseudocysts or retention cysts , which are secondary changes caused by the obstruction in pancreatic ducts , and these pathological features are correlated the imaging findings .