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Invasive Large Duct Type Pancreatic Adenocarcinoma: A Diagnostically Challenging Entity


 
 
 Large duct type invasive pancreatic adenocarcinoma is a morphological variant of pancreatic ductal adenocarcinoma that poses a radiologic and pathologic diagnostic challenge as it closely mimics other non- invasive neoplasms, including mucinous cystic neoplasms and intraductal papillary mucinous neoplasms (IPMN). We report a case of large duct type invasive adenocarcinoma that on radiology closely mimics an IPMN.
 
 
 
 The case id that of a 73-year-old male presenting with weight loss and chronic diarrhea. Abdominal imaging revealed features suggestive of main duct IPMN with possible side branch extension into the pancreatic head. Endoscopic retrograde cholangiopancreatography showed a bile duct stricture that was stented and biopsied, revealing mucinous material with neoplastic cells. A Whipple procedure was performed, revealing a 3.3 cm, tank-pink, papillary lesion in the pancreatic head, that is partially cystic with mucinous contents, and displaying exophytic extension into the main pancreatic duct.
 Microscopically, the lesion consists of a high-grade IPMN involving the main pancreatic duct with side branch extension, and associated with invasive adenocarcinoma, the majority of which is of the large duct type, showing irregularly distributed large ducts with jagged edges and surrounding desmoplasia, with intra-luminal mucinous material and neutrophils. The lining cells show focal pseudo-stratification and bland cytology. Foci of conventional type invasive adenocarcinoma, clusters of invasive tumor cells, and peri-neural invasion are also identified. Post- procedure, the patient underwent chemotherapy with marked symptomatic improvement.
 
 
 
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 Large duct type invasive adenocarcinoma of the pancreas can closely mimic non-invasive pancreatic neoplasms, posing diagnostic challenges that require identification of subtle features to achieve the correct diagnosis and guide treatment.
