IPMN gross appearance. Photographs of four different resected specimens of side-branch IPMNs show the wide variation in appearance of these cystic tumors. a: large, unilocular cystic mass. b: small, unilocular cystic mass. c: ovoid, well-defined cystic mass. d: two small, lobulated cystic masses in the pancreatic head adjacent to the duodenum (arrows)

IPMN gross appearance. Intraoperative photographs with proven diagnosis of IPMNs demonstrate: a: a tortuous mass of multiple, small cysts in the body of the pancreas (arrows). b: a large, unilocular mass in the head of the pancreas adjacent to the duodenum (arrows). Photographs of a surgical specimen from a Whipple procedure (c) demonstrates a multilobulated mass in the head of the pancreas (arrows) and a lobulated cystic mass (d) (arrows) in the head and body of the pancreas from a total pancreatectomy

IPMN internal appearance. Photographs of bivalved side-branch type IPMNs reveal: a: small, unilocular cystic mass (arrows). b: mid-size, unilocular cystic mass with mucoid material and undulating inner surface (arrows). c: mass composed of a few small cysts separated by fibrous septa (arrows). d: multicystic mass filled with mucoid material (arrows)

IPMN internal appearance. Photographs of bivalved side-branch type IPMNs show: a: cystic mass composed of small cysts filled with mucin (arrows). b: ill-defined, partially cystic mass with hemorrhage, mucin, and fibrosis (arrows). c: oligocystic mass with smooth inner lining and fibrosis (arrows). d: ill-defined, yellow, solid mass with areas of fibrosis (arrows)

Major duodenal ampulla appearance in IPMN. Photographs of the ampulla of Vater with IPMNs. a–c: reveal a patulous ampulla with fish eye appearance (arrows) and viscous mucin protruding into the duodenum (arrows). d: photographs (d1–d3) show inspissated mucus being extruded from an IPMN through the ampulla of Vater into the duodenum (arrows)

Photographs show the different mucoid material produced by the IPMNs in different locations. a: protruding from the ampulla of Vater (arrow). b: within the duodenum (arrows). c: protruding from the main pancreatic duct (arrow)

IPMN epithelium subtypes. (a) Intestinal: papilla lined by epithelial cells with basophilic cytoplasm, enlarged oval hyperchromatic nuclei, pseudostratification, and abundant goblet cells. (b) Pancreatobiliary: thin branching papillae lined by cuboidal to columnar cells wtih amphophilic cytoplasm and enlarged hyperchromatic nuclei. (c) Oncocytic: thick branching papilla lined by cells with large, round nuclei, prominent nucleoli, and the characteristic abundant oncocytic cytoplasm. (d) Gastric/Foveolar: papilla lined by columnar epithelium with basally located nuclei and abundant amount of slightly eosinophilic mucinous cytoplasm (H&E, 40×, 60×)

Nonmalignant side-branch-type IPMNs, spectrum of appearances on ultrasound. Conventional ultrasound transverse images in four patients (a–d) show: (a) small, round, unilocular cystic mass (arrow), (b) small, unilocular cystic mass with lobulated margins (arrow), (c) small cystic mass with internal septation (arrow), and (d) small cystic mass with small papillary projection (arrow). Intraoperative ultrasound transverse images in two patients show: (e) large, ovoid, unilocular mass (arrows) and (f) bilobulated cystic mass (arrow)

Malignant side-branch type IPMNs on ultrasound. Intraoperative ultrasound transverse images in two patients. a: shows a complex ovoid mass with cystic and solid components (arrow). b: shows a multilocular cystic mass with thick septa (arrows)

Malignant main duct IPMNs appearance on intraoperative ultrasound (IOUS). Transverse images in three patients demonstrate: a: dilated main pancreatic duct with multiple internal mural nodules (arrows). b: markedly dilated main pancreatic duct with internal projections (arrows). c: c1–c2 images: a large, solid mass with peripheral small cystic components in the head of the pancreas (c1) (arrows) associated with a dilated main pancreatic duct containing internal projections (c2) (arrows)

IPMNs solid appearance on intraoperative ultrasound (IOUS). Intraoperative ultrasound transverse images (a, b) demonstrate a round, well-demarcated, mostly solid mass with small cystic components in the head of the pancreas (arrows)

IPMNs appearance on endoscopic ultrasound (EUS) in four patients. Transverse images demonstrate: a: a unilocular cystic mass (arrows). b: a cystic mass with internal projections (arrow). c: a complex mass with solid and cystic components (arrows). d: a mostly solid, heterogeneous mass (arrows)

Nonmalignant side-branch type IPMNs, spectrum of appearances on CT. CECT axial images demonstrate: Patient a: a multilocular cystic mass in the uncinate process (arrows). Patient b: a tubular-like appearance cystic mass in the uncinate process (arrow). Patient c: a unilocular cystic mass in the body of the pancreas (arrow). Patient d: a bilobulated cystic mass in the head of the pancreas (arrows)

Nonmalignant side-branch type IPMNs, spectrum of appearances on MR. a: single-shot fast spin echo T2-weighted axial image shows a cystic mass with finger-like tubular appearance involving the uncinate process (arrow). b: MRCP thick slab image shows a mass composed of multiple small cysts (arrow). c: MRCP thick slab image shows a multilocular cystic mass in the uncinate process (arrow). d: MRCP thick slab image shows a tubular cystic mass involving the body of the pancreas (arrow). a–d: note the communication of each mass with the main pancreatic duct (arrowheads)

Main duct-type IPMNs appearance on CT. CECT axial images show: Patient a: diffuse, dilated pancreatic duct (arrows). Patient b: markedly diffuse, dilated main pancreatic duct with intraluminal low-density amorphous material (arrows). Patients a, b: note the atrophy of the pancreatic parenchyma associated with each mass

Main duct-type IPMNs appearance on MR. a: MRCP coronal image (MIP) reveals a markedly diffuse dilated main pancreatic duct (arrows) and associated diffuse dilatation of the intra- and extrahepatic biliary system (curved arrow). b: single-shot fast spin echo T2-weighted axial image reveals a diffuse, markedly dilated main pancreatic duct (arrows). a, b: note the diffuse atrophy of the pancreatic parenchyma associated with each mass

Combined-type IPMNs appearance on CT. CECT axial images show: Patient a: a multilocular cystic mass in the uncinate process (arrows) extending into the main pancreatic duct (arrowhead). Patient b: a cluster of dilated tubular structures in the body of the pancreas (arrows) extending into the main pancreatic duct (arrowheads)

Combined-type IPMNs appearance on MR. Patient a: MRCP thick slab image shows two lobulated cystic masses in the uncinate process (arrows) extending into the main pancreatic duct (arrowhead). Patient b: single-shot fast spin echo axial image shows a multilocular cystic mass in the body of the pancreas (arrows), extending into the main pancreatic duct (arrowhead)

Multifocal IPMNs appearance on MR. Patients a, b: MRCP thick slab images show multiple, small cystic masses throughout the pancreas (arrows). Patients c, d: single-shot fast spin echo T2-weighted images show multiple, small cystic masses throughout the pancreas (arrows)

Findings suggestive of IPMNs malignant transformation on CT. CECT axial images of four patients: Patient a: dilated main pancreatic duct with a mural nodule (arrows). Patient b: dilated main pancreatic duct with multiple intramural nodules (arrows). Patient c: focal area of pancreatic parenchyma enhancement (arrow) associated with a dilated main pancreatic duct and atrophy of the pancreas. Patient d: large cystic pancreatic mass extending into the main pancreatic duct (arrows)

Findings suggestive of IPMNs malignant transformation on MR. MR images of three patients. Patient (a): single-shot fast spin echo T2-weighted axial images (a1–a2) show a large multilocular cystic mass with small internal mural nodules (arrows). Patient b: fat-suppressed T2-weighted axial image shows a complex cystic mass with thick, irregular low signal papillary growths (arrows) associated with dilatation of the pancreatic duct. Patient c: fat-suppressed contrast-enhanced T1-weighted axial image shows a large cystic mass with enhancing papillary nodules involving the head of the pancreas (arrows)

Side-branch type, borderline IPMN on CT. A 79-year-old male with a 2-year history of a cystic lesion of the pancreas that had been followed by serial CTs. On the last study, it was noted that the lesion had doubled in size. Patient had also experienced a 10 lb weight loss. CECT axial images (a, b) show a multilobulated cystic mass involving the head and uncinate process of the pancreas (arrows). Photograph of the resected gross specimen (c) shows a well-defined, ovoid mass with smooth serosal surface (arrows) adjacent to the duodenum. Photograph of the bisected ovoid mass (d) shows a cystic tumor with smooth internal lining and thin fibrous septa (arrows). On microscopic examination (e) (H&E, 10×) the cyst was lined by benign foveolar-type epithelium with tall columnar cells, basally located nuclei, and abundant mucinous cytoplasm. The tumor cells are strongly positive for MUC-5 (f) by immunohistochemistry (immunostain, 10×)

Side-branch type adenoma IPMN on CT and MR. A 67-year-old male complaining of mild epigastric pain. A conventional abdominal ultrasound (not shown) revealed a mass in the head of the pancreas. The patient underwent an endoscopic ultrasound with fine-needle aspiration that suggested a mucinous pancreatic tumor. CECT axial image (a) shows a small multicystic mass (arrows) involving the uncinate process. The patient underwent a pyloric-sparing Whipple procedure. Photograph of the gross specimen (b) shows a multilocular cystic mass in the head of the pancreas (arrows)

Side-branch type IPMN on CT. A 63-year-old male with an incidental finding on a CT of the abdomen performed to evaluate a complicated inguinal hernia revealing a pancreatic mass. Endoscopic ultrasound with fine-needle aspiration showed a 35 mm cystic lesion with internal septa containing a solid component and other areas with possible papillary formations and a viscous, mucinous fluid, difficult to aspirate. No communication with the pancreatic duct was demonstrated. CECT axial (a, b) and coronal (c, d) images show a multilobular cystic mass in the uncinate process of the pancreas (arrows). T2-weighted axial image (e) shows a mass with high signal intensity (arrow), and MRCP reformatted coronal image (f) shows a multicystic mass in the uncinate process communicating with pancreatic duct (arrow). The patient underwent a pyloric-sparing Whipple procedure. Photograph of the surgical specimen (g) shows a lobulated mass (arrow). Photograph of the sectioned gross specimen (h) shows a cystic mass filled with a thick mucinous material (arrows). Final pathology (i): IPMN with intermediate- to high-grade dysplasia, side-branch type (H&E, 20×)