Intraductal papillary neoplasm of the bile duct: diagnostic value of MRI features in differentiating pathologic subclassifications-type 1 versus type 2 Jeon SK, Lee JM, Yoo J, Park S, Joo I, Yoon JH, Lee KB. Eur Radiol. 2023 Dec 19. doi: 10.1007/s00330-023-10491-9. PMID: 38114846. Intraductal papillary neoplasm of the bile duct (IPNB) is a grossly visible predominantly intraductal-growing papillary neoplasm, which includes villous structures in the dilated bile ducts and is covered by well-differentiated neoplastic epithelium with fine fibrovascular cores.1 IPNB has a prevalence of 4-15% among bile duct tumors, and thus, is considered a relatively rare disease. In 2019, the World Health Organization adopted a new classification of IPNBs based on their histological similarity to intraductal papillary mucinous neoplasm (IPMN), defining two categories, type I IPNB, which is histologically similar to IPMN, and type II IPNB, which has a more complex histology.2 The ability to differentiate between type I and type II IPNB is crucial, as type I IPNBs have better survival rates. 3 Regarding therapy, curative resection with negative margins is the optimal approach, therefore imaging is of outmost importance to the precision of the surgical procedure, as it provides a comprehensive understanding of the tumor’s location and extent. Magnetic resonance imaging (MRI) with MR cholangiopancreatography (MRCP) is the modality of choice for the evaluation of various biliary diseases, and along with diffusion-weighted imaging, has been helpful in differentiating IPNBs with stromal invasion. This study is the first, to our knowledge, to compare the clinical and MRI features between type I and type II IPNBs based on the new pathologic criteria and try to distinguish the two IPNB subtypes using imaging entirely. The study included 60 patients with pathologically proven IPNBs via surgery and available preoperative contrast-enhanced MRI with MRCP within two months of the surgery. The authors analyzed the following MRI qualitative and quantitative features: i. Tumor location, ii. The presence or absence of an intraductal visible mass, iii. Multiplicity of the tumor, iv. Bile duct dilatation (isolated upstream bide duct dilatation versus bot upstream and downstream bile duct dilatation), v. bile duct wall thickening, vi. Adjacent organ invasions, vii. Longitudinal tumor size along the bile duct when applicable and viii. The contrast enhancement ratio of the tumor.
| The results demonstrated that extrahepatic location, no dilatation of the tumor-bearing segment of the bile duct and isolated upstream bile duct dilatation were indicative of type II IPNB, as well as that an associated invasive carcinoma was more frequently found in type II than type I IPNB. Furthermore, papillary shape of the tumor in the patients with a visible intraductal mass was observed more frequently in patients with type I IPNBs, compared to the smooth nodular shape that was seen in type II IPNBs. All in all, the most significant MRI features for discriminating type II IPNB from type I IPNB were tumor location and dilatation of tumor-bearing segment of the bile duct, which, combined, yielded a sensitivity of 65% and a specificity of 95%. Consequently, although MRI with MRCP cannot be absolute in differentiating IPNB types, it may be helpful in certain cases, and prove crucial in the management and treatment of patients with IPNBs. Jeon SK et al. have laid the foundation for future advancements in the understanding of IPNBs and further studies that may clarify to a greater extent the most important MRI features in distinguishing type I and type II IPNBs. References
Georgios Giannis is a second-year Radiology Resident at "Konstantopouleio Hospital" in Athens, Greece. He completed his undergraduate medical training at the National and Kapodistrian University of Athens. He has a wide range of interests in diagnostic imaging, especially regarding the hepatobiliary system. Comments may be sent to giorgosgiannis42@gmail.com |
June 2024
