Pancreatic ductal adenocarcinoma with intratumoral cystic lesions on MRI: correlation with histopathological findings

The purpose of this study was to evaluate intratumoral cystic lesions of pancreatic ductal adenocarcinoma (PDAC) depicted on MRI, and to correlate these cystic lesions with their histopathological findings. This study included 12 patients (7 males and 5 females; mean age, 59 years) with intratumoral cystic lesions of PDAC detected on a retrospective MRI review. We reviewed the histopathological findings of the cystic lesions within PDACs and analysed the MRI findings, focusing on the appearance of the intratumoral cystic lesions, i.e. the size, number, margin and intratumoral location, and on the ancillary findings of PDAC, i.e. peripancreatic infiltration, upstream pancreatic duct dilatation and distal parenchymal atrophy. Intratumoral cystic lesions were classified as neoplastic mucin cysts (n = 7, 58%) or cystic necrosis (n = 5, 42%) according to the histopathological findings; they ranged in greatest dimension from 0.5 cm to 3.4 cm (mean, 1.7 cm). Seven patients had only one cystic lesion each, while the remaining five had multiple cystic lesions. Most of the neoplastic mucin cysts had smooth margins (n = 6, 86%) and eccentric locations (n = 6), whereas most cystic necroses had irregular margins (n = 4, 80%) and centric locations (n = 4). The most common ancillary findings of PDAC were peripancreatic infiltration, distal pancreatic atrophy and upstream pancreatic duct dilatation (92%, 75% and 58%, respectively). The intratumoral cystic lesions of PDACs on MRI were classified as either neoplastic mucin cysts with smooth margins and eccentric locations or cystic necroses with irregular margins and centric locations.Pancreatic cancer is the fifth leading cause of cancer-related death in both men and women and is responsible for 5% of all cancer-related deaths in the United States 1]. Despite the advances in surgical techniques, as well as the major improvements in chemotherapy and radiotherapy protocols, the prognosis of pancreatic ductal adenocarcinoma (PDAC) usually implies a 1-year survival rate of <20% and a 5-year survival rate of <5% 2].PDAC typically presents as an irregular solid tumour with a scirrhous character resulting from a prominent desmoplastic reaction. However, recent studies have shown that PDAC may be accompanied by cystic changes within or adjacent to the mass, and that the incidence of PDAC with cystic changes ranges from <1% to 8% 3, 4]. Radiologists should be familiar with PDACs with cystic changes as they may resemble more common cystic pancreatic lesions, such as pseudocysts, intraductal papillary mucinous neoplasms (IPMNs), solid pseudopapillary tumours and non-functioning islet cell tumours, all of which are managed differently and usually have better patient survival rates 5–7].Many studies have discussed the radiological appearance of PDAC accompanied by cystic lesions 6–11]. Most of these studies have discussed pseudocysts or retention cysts depicted adjacent to the PDAC or in the extrapancreatic area in the clinical setting of pancreatitis 8–11], whereas only a few studies have discussed intratumoral cystic lesions, such as cystic necroses, in larger ordinary PDACs 6, 7]. Some case reports have described the intratumoral cystic changes of PDAC variants, i.e. adenosquamous carcinoma 12], mucinous adenocarcinoma (colloid or mucinous non-cystic carcinoma) 13], osteoclast-like giant cell carcinoma 14] and pleomorphic giant cell carcinoma 15]. To the best of our knowledge, there have been no radiological reports regarding the intratumoral cystic lesions of ordinary PDAC. Compared with CT, MRI has the advantage of being able to detect cystic changes within pancreatic masses and to provide more accurate morphological detail on these changes 16]. Therefore, the aims of this study were to evaluate intratumoral cystic lesions of ordinary PDAC detected on MRI and to correlate the cystic lesions with their histopathological findings.