The intraductal oncocytic papillary neoplasm (IOPN) is one of the intraductal papillary neoplasms of the pancreaticobiliary system by the current WHO classification. It is rare but specific intraductal papillary neoplasm. IOPN tends to occur in the main pancreatic duct of elderly males. It is a cystic epithelial neoplasm with nodular intracystic projections. IOPN is composed of oncocytic cells with a granular cytoplasm rich in mitochondria. IOPN typically shows high-grade dysplasia and is positive immunohistochemically for Muc-1, Muc-5AC, and Muc-6. It is also reportedly positive for Heppar-1 and CD-117, although invasive component from IOPN may become negative for CD-117. IOPN lacks the most common genetic alterations that characterize pancreatic ductal adenocarcinoma and the other types of intraductal papillary mucinous neoplasm, such as K ras and GNA S somatic mutations. Instead, IOPN harbors PRKAC-A and PRKAC-B fusion genes as the genetic hallmark which is distinctively absent in other intraductal papillary neoplasms of the pancreaticobiliary system. Although IOPN is associated with invasive carcinoma in up to 30% of cases, and the local recurrence rate is up to 40%, survival outcome is extremely favorable even after a second resection, with a five-year disease survival rate approaching 100%. Thus, it is important to identify an invasive pancreatic adenocarcinoma arising from IOPN.
Feature Summary of intraductal oncocytic papillary neoplasm (IOPN):
A unique and rare intraductal papillary neoplasm of the pancreaticobiliary system.
Confluent papillary growth of oncocytic cells with ample eosinophilic cytoplasm.
Usually, high-grade dysplasia and 30% of cases harbor invasive carcinoma.
Positive for CD117 is a unique feature.
Also positive for Muc-1, Muc-5AC and Muc-6.
PRKAC-A and PRKAC-B gene fusion is a distinct genetic hallmark.
Extremely favorable survival outcome after resection.
References
Singhi, Aatur D et al. “Recurrent Rearrangements in PRKACA and PRKACB in Intraductal Oncocytic Papillary Neoplasms of the Pancreas and Bile Duct.” Gastroenterology vol. 158,3 (2020): 573-582.e2. doi:10.1053/j.gastro.2019.10.028
Mattiolo, Paola et al. “CD117 Is a Specific Marker of Intraductal Papillary Mucinous Neoplasms (IPMN) of the Pancreas, Oncocytic Subtype.” International journal of molecular sciences vol. 21,16 5794. 12 Aug. 2020, doi:10.3390/ijms21165794
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