(Radiographics. 2001;21:323-337.)
© RSNA, 2001
Radiologic Spectrum of Intraductal Papillary Mucinous Tumor of the Pancreas1
Jae Hoon Lim, MD,
Gina Lee, MD and
Young Lyun Oh, MD
1 From the Departments of Radiology (J.H.L., G.L.) and Diagnostic Pathology (Y.L.O.), Sungkyunkwan University School of Medicine, Samsung Medical Center, 50 Ilwon-dong, Kangnam-ku, Seoul, Korea 135-710. Recipient of a Cum Laude award for a scientific exhibit at the 1999 RSNA scientific assembly. Received February 28, 2000; revision requested May 8 and received May 29; accepted June 1. Address correspondence to J.H.L. (e-mail: jhlim@smc.samsung.co.kr).
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Abstract
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"Intraductal papillary mucinous tumor" is now the preferred term to describe a spectrum of proliferation of the pancreatic ductal epithelium. The tumor produces an excessive amount of mucin and results in progressive dilation of the main pancreatic duct or cystic dilation of the branch ducts, depending on the location of the tumor. This tumor is small and localized in a segment of the main pancreatic duct or in branch ducts, particularly in the branch ducts of the uncinate process, but it may also be diffuse, involving a wide area of the pancreatic ducts. Excessive mucin may impede the pancreatic duct flow and, in turn, produce symptoms of chronic pancreatitis. The following findings are seen on imaging studies: lobulated multicystic dilatation of the branch ducts, diffuse dilatation of the main pancreatic duct, intraductal papillary tumors, elongated or globlike mucous plugs in the dilated ducts, and bulging of the papilla into the duodenal lumen. The diagnosis is suggested at ultrasonography, computed tomography, or magnetic resonance cholangiopancreatography. Endoscopic retrograde cholangiopancreatography is the imaging modality of choice for the diagnosis, because it depicts the communication between the cystically dilated branch ducts and the diffusely dilated main pancreatic duct, as well as intraductal papillary tumor and mucous plugs.
Index Terms: Endoscopic retrograde cholangiopancreatography (ERCP), 77.1222 • Pancreas, CT, 77.1211 • Pancreas, cysts, 77.3125 • Pancreas, MR, 77.1214 • Pancreas, neoplasms, 77.3124, 77.3125 • Pancreas, US, 77.1298 • Pancreatic ducts, 77.3124, 774.3125
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Introduction
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Intraductal papillary mucinous tumor (IPMT) of the pancreas is characterized by the presence of mucin-producing tumor and cystic dilation of the branches of the pancreatic duct in the uncinate process (branch duct type), diffuse or segmental dilatation of the main pancreatic duct (main duct type), or dilatation of the main duct and the branch ducts (combined type) (1)–(3) (Fig 1). The dilated ducts often contain profuse mucin. This tumor is also known as mucin-producing pancreatic tumor (4),(5), mucinous ductal ectasia (6)–(10), intraductal mucin-hypersecreting tumor (3),(11), 12, or ductectatic mucinous cystic tumor (13)–(15). The unified term IPMT was adopted in 1997 (16)–(19). The relative frequency of each type of tumor on the basis of a large number of cases has not been reported in the literature, to our knowledge. Among the 18 patients in our study, eight had branch duct type tumors, seven had main duct type, and three had combined type.
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Figure 1a. Drawings depict three types of IPMT of the pancreas: branch duct type (a), main duct type (b), and combined type (c). a = adenocarcinoma, b = adenoma, c = hyperplasia, m = mucus.
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Figure 1b. Drawings depict three types of IPMT of the pancreas: branch duct type (a), main duct type (b), and combined type (c). a = adenocarcinoma, b = adenoma, c = hyperplasia, m = mucus.
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Figure 1c. Drawings depict three types of IPMT of the pancreas: branch duct type (a), main duct type (b), and combined type (c). a = adenocarcinoma, b = adenoma, c = hyperplasia, m = mucus.
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Histologically, the lesions can represent a spectrum of abnormalities from simple hyperplasia to papillary adenoma and carcinoma, and different histologic grades frequently coexist (3),(15). The tumor is usually small and flat (Fig 2a) and is characterized by the presence of innumerable papillae (Fig 2b) coated with columnar epithelium (Fig 2c). Hyperplasia, dysplasia, or adenoma may undergo malignant transformation over time, often many years (3). Tumor or hyperplasia may be present in a limited area in the dilated ducts, but it frequently extends along the main ducts or branch ducts and eventually involves almost all of the adjacent branch ducts (20) (Fig 1). Because this condition does not cause any specific symptoms or may be misdiagnosed as chronic pancreatitis, the lesion may escape detection, and ductal dilatation is usually prominent when it is finally detected (3).
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Figure 2a. Gross and histopathologic findings of IPMTs. (a) Photograph of the resected specimen shows two elevated intraductal papillary tumors (straight arrows) in the dilated branch duct of the uncinate process. Note other small cystically dilated branch ducts (curved arrows). (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows intraductal papillary adenoma in a dilated branch duct (arrows). The tumor consists of a myriad of papillary projections. Note the intervening septa (arrowheads) that separate the mucin-filled lacuna. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of intraductal papillary adenoma and combined papillary hyperplasia shows multiple papillary projections covered with columnar epithelial cells. The term papillary originates from these papillary projections.
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Figure 2b. Gross and histopathologic findings of IPMTs. (a) Photograph of the resected specimen shows two elevated intraductal papillary tumors (straight arrows) in the dilated branch duct of the uncinate process. Note other small cystically dilated branch ducts (curved arrows). (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows intraductal papillary adenoma in a dilated branch duct (arrows). The tumor consists of a myriad of papillary projections. Note the intervening septa (arrowheads) that separate the mucin-filled lacuna. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of intraductal papillary adenoma and combined papillary hyperplasia shows multiple papillary projections covered with columnar epithelial cells. The term papillary originates from these papillary projections.
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Figure 2c. Gross and histopathologic findings of IPMTs. (a) Photograph of the resected specimen shows two elevated intraductal papillary tumors (straight arrows) in the dilated branch duct of the uncinate process. Note other small cystically dilated branch ducts (curved arrows). (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows intraductal papillary adenoma in a dilated branch duct (arrows). The tumor consists of a myriad of papillary projections. Note the intervening septa (arrowheads) that separate the mucin-filled lacuna. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of intraductal papillary adenoma and combined papillary hyperplasia shows multiple papillary projections covered with columnar epithelial cells. The term papillary originates from these papillary projections.
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The clinical symptoms and signs of IPMT are due to the gradual distention of the excretory duct that is induced by the hypersecretion of mucin. The impaired outflow of pancreatic juice may cause pain and produces the laboratory test abnormalities of pancreatitis (3). Diagnosis is made on the basis of imaging studies that show the characteristic dilatation of the branches or main duct of the pancreas and endoscopic studies that demonstrate thick mucin protruding through the bulging patulous duodenal papilla (3),(4) (Fig 3).
IPMT is considered a low-grade malignancy, especially the hyperplastic or adenomatous variety, but clinical behaviors regarding the degree of malignancy and prognosis for the various types are not fully known because the disease was first described relatively recently (5),(15). Total resection is the treatment of choice for the main duct type (20). Local resection is often sufficient for main duct type with segmental involvement. In cases of the branch duct type, total resection should be performed when the main pancreatic duct is dilated. Close monitoring may be considered for small cystic lesions less than 2.5 cm in diameter and with a normal main pancreatic duct, because such lesions are usually benign and grow very slowly (20).
In this article, the imaging findings of IPMT are illustrated on the basis of gross and histopathologic findings, the strengths and weaknesses of each diagnostic modality in the evaluation of this disease are discussed, and the differential diagnosis from chronic pancreatitis or other cystic pancreatic diseases is described.
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Radiologic Findings
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IPMT, Branch Duct Type
The branch duct type of IPMT usually occurs in the uncinate process of the pancreas but may also occur in the body and tail (3),(6),(20). Macroscopically, the lesion is covered with thin pancreatic parenchyma and consists of conglomerated communicating cysts 1–2 cm in diameter (1)–(3),(20). Multiple septa separate fluid-filled lacuna within which is either tumor, mucin, or both (Fig 2b). The tumor may be limited to one of the branch ducts and may produce a unilocular cyst. More or less marked dilatation of the main pancreatic duct is often associated, because mucus impedes the drainage of pancreatic juice through the distal pancreatic duct (3),(6)–(15),(20).
At computed tomography (CT), ultrasonography (US), or magnetic resonance cholangiopancreatography (MRCP), the tumor appears as clustered small cysts with a lobulated margin possessing septa (Figs 4, 5) or as a single unilocularcystic lesion (1)–(3),(5),(6),(10),(12),(13),(20),(21) (Fig 6). The intraductal mass is frequently not seen because the tumor is flat (Fig 5). The main pancreatic duct may also be dilated due to mucin, which is not usually visible (Figs 4, 5). The pancreatic atrophy may be severe (20) (Fig 4).
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Figure 4a. Intraductal papillary mucinous adenoma, branch duct type, in a 60-year-old man. (a, b) US (a) and CT (b) scans show a cystic lesion with solid components (arrows) at the uncinate process. The main pancreatic duct (arrowheads) is dilated. (c) ERCP image shows the dilated main pancreatic duct and intraductal globular filling defects due to mucus (arrows). The cystically dilated branch duct is not opacified owing to obstruction by a thick mucous plug. (d) Photograph of the resected specimen shows the cystically dilated branch ducts opened. The internal surface is rough, and there are multiple elevated papillary adenomas (black arrows). White arrow points to communicating channel to another cystic space. Ruler indicates millimeters.
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Figure 4b. Intraductal papillary mucinous adenoma, branch duct type, in a 60-year-old man. (a, b) US (a) and CT (b) scans show a cystic lesion with solid components (arrows) at the uncinate process. The main pancreatic duct (arrowheads) is dilated. (c) ERCP image shows the dilated main pancreatic duct and intraductal globular filling defects due to mucus (arrows). The cystically dilated branch duct is not opacified owing to obstruction by a thick mucous plug. (d) Photograph of the resected specimen shows the cystically dilated branch ducts opened. The internal surface is rough, and there are multiple elevated papillary adenomas (black arrows). White arrow points to communicating channel to another cystic space. Ruler indicates millimeters.
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Figure 4c. Intraductal papillary mucinous adenoma, branch duct type, in a 60-year-old man. (a, b) US (a) and CT (b) scans show a cystic lesion with solid components (arrows) at the uncinate process. The main pancreatic duct (arrowheads) is dilated. (c) ERCP image shows the dilated main pancreatic duct and intraductal globular filling defects due to mucus (arrows). The cystically dilated branch duct is not opacified owing to obstruction by a thick mucous plug. (d) Photograph of the resected specimen shows the cystically dilated branch ducts opened. The internal surface is rough, and there are multiple elevated papillary adenomas (black arrows). White arrow points to communicating channel to another cystic space. Ruler indicates millimeters.
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Figure 4d. Intraductal papillary mucinous adenoma, branch duct type, in a 60-year-old man. (a, b) US (a) and CT (b) scans show a cystic lesion with solid components (arrows) at the uncinate process. The main pancreatic duct (arrowheads) is dilated. (c) ERCP image shows the dilated main pancreatic duct and intraductal globular filling defects due to mucus (arrows). The cystically dilated branch duct is not opacified owing to obstruction by a thick mucous plug. (d) Photograph of the resected specimen shows the cystically dilated branch ducts opened. The internal surface is rough, and there are multiple elevated papillary adenomas (black arrows). White arrow points to communicating channel to another cystic space. Ruler indicates millimeters.
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Figure 5a. Intraductal papillary mucinous adenoma and hyperplasia, branch duct type, in a 64-year-old man. (a, b) US (a) and CT (b) scans of the pancreas head show a cystically dilated branch duct with septa at the uncinate process. Note the dilated branch ducts of the uncinate process (arrows). In a, A = aorta, I = inferior vena cava, P = pancreas head, S = superior mesenteric vein. (c) Coronal T1-weighted MR image (repetition time/echo time = 70/4.2) shows clustered cystic lesion with thin septa (arrows) at the uncinate process. (d) ERCP image shows cystically dilated branch ducts of the uncinate process (open arrow). The main duct is also dilated. Note the filling defects in the dilated branch ducts, which represent mucin (solid arrows).
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Figure 5b. Intraductal papillary mucinous adenoma and hyperplasia, branch duct type, in a 64-year-old man. (a, b) US (a) and CT (b) scans of the pancreas head show a cystically dilated branch duct with septa at the uncinate process. Note the dilated branch ducts of the uncinate process (arrows). In a, A = aorta, I = inferior vena cava, P = pancreas head, S = superior mesenteric vein. (c) Coronal T1-weighted MR image (repetition time/echo time = 70/4.2) shows clustered cystic lesion with thin septa (arrows) at the uncinate process. (d) ERCP image shows cystically dilated branch ducts of the uncinate process (open arrow). The main duct is also dilated. Note the filling defects in the dilated branch ducts, which represent mucin (solid arrows).
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Figure 5c. Intraductal papillary mucinous adenoma and hyperplasia, branch duct type, in a 64-year-old man. (a, b) US (a) and CT (b) scans of the pancreas head show a cystically dilated branch duct with septa at the uncinate process. Note the dilated branch ducts of the uncinate process (arrows). In a, A = aorta, I = inferior vena cava, P = pancreas head, S = superior mesenteric vein. (c) Coronal T1-weighted MR image (repetition time/echo time = 70/4.2) shows clustered cystic lesion with thin septa (arrows) at the uncinate process. (d) ERCP image shows cystically dilated branch ducts of the uncinate process (open arrow). The main duct is also dilated. Note the filling defects in the dilated branch ducts, which represent mucin (solid arrows).
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Figure 5d. Intraductal papillary mucinous adenoma and hyperplasia, branch duct type, in a 64-year-old man. (a, b) US (a) and CT (b) scans of the pancreas head show a cystically dilated branch duct with septa at the uncinate process. Note the dilated branch ducts of the uncinate process (arrows). In a, A = aorta, I = inferior vena cava, P = pancreas head, S = superior mesenteric vein. (c) Coronal T1-weighted MR image (repetition time/echo time = 70/4.2) shows clustered cystic lesion with thin septa (arrows) at the uncinate process. (d) ERCP image shows cystically dilated branch ducts of the uncinate process (open arrow). The main duct is also dilated. Note the filling defects in the dilated branch ducts, which represent mucin (solid arrows).
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Figure 6a. Intraductal papillary mucinous hyperplasia, branch duct type, in a 60-year-old man. Transverse oblique US (a) and CT (b) scans show an ovoid cystic lesion (arrows). Note tiny punctate parenchymal calcification (arrowheads) caused by chronic pancreatitis. (Case courtesy of Kenichi Takayasu, MD, National Cancer Center, Tokyo, Japan.)
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Figure 6b. Intraductal papillary mucinous hyperplasia, branch duct type, in a 60-year-old man. Transverse oblique US (a) and CT (b) scans show an ovoid cystic lesion (arrows). Note tiny punctate parenchymal calcification (arrowheads) caused by chronic pancreatitis. (Case courtesy of Kenichi Takayasu, MD, National Cancer Center, Tokyo, Japan.)
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At endoscopic retrograde cholangiopancreatography (ERCP), the branch ducts are cystically dilated (Figs 5, 7). Mucin is frequently depicted as elongated bandlike (Fig 8), threadlike, or sometimes nodular filling defects (Figs 4, 5, 7) in the dilated ducts (3). Duodenal endoscopy at the time of ERCP reveals a patulous orifice of the duodenal papilla through which thick mucus protrudes (Fig 3). The duodenal papilla protrudes into the lumen of the duodenum, which can be demonstrated at CT (Fig 8) or MR imaging (20),(21). Bulging duodenal papilla and severe dilatation of the main pancreatic duct are more frequent in the malignant form (21), but differentiation of benign from malignant IPMT is generally difficult. Papillary carcinoma may sometimes invade the main pancreatic duct and bile ducts and cause obstruction. In such cases, the dilatation is not due to IPMT per se but to obstruction caused by the carcinoma. Therefore, it is impossible to differentiate between the diffuse involvement of the pancreatic duct and simple dilation due to obstruction (20).
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Figure 7a. IPMT, branch duct type, in a 67-year-old woman. (a) CT scan shows two small discrete cystic lesions in the body of the pancreas. Small cysts were seen at the head of the pancreas (not shown). (b) MRCP image (11.9/95.0) shows lobulated clustered cysts in the head and tail of the pancreas. Note a small cyst (arrow) in the body of the pancreas. (c) ERCP image shows clustered cysts in the head and body of the pancreas (open arrows). The main pancreatic duct at the tail is not opacified owing to blockage by a mucin plug at the orifice of the cysts (solid arrow). Note faint filling defects (arrowheads) in the cysts, which represent mucus.
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Figure 7b. IPMT, branch duct type, in a 67-year-old woman. (a) CT scan shows two small discrete cystic lesions in the body of the pancreas. Small cysts were seen at the head of the pancreas (not shown). (b) MRCP image (11.9/95.0) shows lobulated clustered cysts in the head and tail of the pancreas. Note a small cyst (arrow) in the body of the pancreas. (c) ERCP image shows clustered cysts in the head and body of the pancreas (open arrows). The main pancreatic duct at the tail is not opacified owing to blockage by a mucin plug at the orifice of the cysts (solid arrow). Note faint filling defects (arrowheads) in the cysts, which represent mucus.
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Figure 7c. IPMT, branch duct type, in a 67-year-old woman. (a) CT scan shows two small discrete cystic lesions in the body of the pancreas. Small cysts were seen at the head of the pancreas (not shown). (b) MRCP image (11.9/95.0) shows lobulated clustered cysts in the head and tail of the pancreas. Note a small cyst (arrow) in the body of the pancreas. (c) ERCP image shows clustered cysts in the head and body of the pancreas (open arrows). The main pancreatic duct at the tail is not opacified owing to blockage by a mucin plug at the orifice of the cysts (solid arrow). Note faint filling defects (arrowheads) in the cysts, which represent mucus.
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Figure 8a. IPMT, branch duct type, in a 59-year-old man. (a) CT image shows the dilated main pancreatic duct and bulging of the papilla into the duodenal lumen (arrow). (b) ERCP image shows a cystically dilated branch duct (open arrow) and the main pancreatic duct containing bandlike filling defects caused by mucus (solid arrows).
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Figure 8b. IPMT, branch duct type, in a 59-year-old man. (a) CT image shows the dilated main pancreatic duct and bulging of the papilla into the duodenal lumen (arrow). (b) ERCP image shows a cystically dilated branch duct (open arrow) and the main pancreatic duct containing bandlike filling defects caused by mucus (solid arrows).
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IPMT, Main Duct Type
Although tumor or hyperplasia may reside in an area along the main pancreatic duct, the entire pancreatic duct is dilated because profuse mucin impedes the flow of juice through the pancreatic duct (Fig 9). There may also be segmental involvement (3),(20). At US, CT, and MRCP, the entire main pancreatic duct is moderately or markedly dilated (Figs 9, 10). There may be some excrescences in the dilated ducts, representing papillary tumor (20),(21), but they are usually difficult to visualize because the tumor is small and flat (Fig 9). As in the branch duct type, duodenal papilla may protrude into the duodenal lumen. Mucin is usually difficult to demonstrate. At ERCP, the entire pancreatic duct is dilated, and there may be filling defects of mucin or tumor excrescence (Figs 9, 10). When the mucin plug is globular or nodular, it is difficult to differentiate from a papillary tumor (20).
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Figure 9a. IPMT of borderline malignancy and focal carcinomatous change, main duct type, in a 37-year-old woman. (a-c) US (a), CT (b), and MRCP (2,317.8/185.8) (c) images show the markedly dilated main pancreatic duct. No mass or mucus is demonstrated. (d) ERCP image shows the markedly dilated main pancreatic duct with elongated filling defects (straight arrows) and an ill-defined scalloped margin (curved arrows) representing intraductal mucus or tumor. (e) Duodenal endoscopic image shows thick mucus (*) protruding through the patulous duodenal papilla, which is bulging (arrows). (f) Photograph of the resected pancreas shows the dilated main duct (*) opened. A flat elongated tumor (hyperplasia and borderline malignancy) with a rough surface (arrows), 8 cm long and 1 cm wide, covers a wide area of the dilated main duct in the region of the pancreas body and tail. At microscopic study (not shown), focal areas of malignant change with stromal invasion were identified.
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Figure 9b. IPMT of borderline malignancy and focal carcinomatous change, main duct type, in a 37-year-old woman. (a-c) US (a), CT (b), and MRCP (2,317.8/185.8) (c) images show the markedly dilated main pancreatic duct. No mass or mucus is demonstrated. (d) ERCP image shows the markedly dilated main pancreatic duct with elongated filling defects (straight arrows) and an ill-defined scalloped margin (curved arrows) representing intraductal mucus or tumor. (e) Duodenal endoscopic image shows thick mucus (*) protruding through the patulous duodenal papilla, which is bulging (arrows). (f) Photograph of the resected pancreas shows the dilated main duct (*) opened. A flat elongated tumor (hyperplasia and borderline malignancy) with a rough surface (arrows), 8 cm long and 1 cm wide, covers a wide area of the dilated main duct in the region of the pancreas body and tail. At microscopic study (not shown), focal areas of malignant change with stromal invasion were identified.
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Figure 9c. IPMT of borderline malignancy and focal carcinomatous change, main duct type, in a 37-year-old woman. (a-c) US (a), CT (b), and MRCP (2,317.8/185.8) (c) images show the markedly dilated main pancreatic duct. No mass or mucus is demonstrated. (d) ERCP image shows the markedly dilated main pancreatic duct with elongated filling defects (straight arrows) and an ill-defined scalloped margin (curved arrows) representing intraductal mucus or tumor. (e) Duodenal endoscopic image shows thick mucus (*) protruding through the patulous duodenal papilla, which is bulging (arrows). (f) Photograph of the resected pancreas shows the dilated main duct (*) opened. A flat elongated tumor (hyperplasia and borderline malignancy) with a rough surface (arrows), 8 cm long and 1 cm wide, covers a wide area of the dilated main duct in the region of the pancreas body and tail. At microscopic study (not shown), focal areas of malignant change with stromal invasion were identified.
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Figure 9d. IPMT of borderline malignancy and focal carcinomatous change, main duct type, in a 37-year-old woman. (a-c) US (a), CT (b), and MRCP (2,317.8/185.8) (c) images show the markedly dilated main pancreatic duct. No mass or mucus is demonstrated. (d) ERCP image shows the markedly dilated main pancreatic duct with elongated filling defects (straight arrows) and an ill-defined scalloped margin (curved arrows) representing intraductal mucus or tumor. (e) Duodenal endoscopic image shows thick mucus (*) protruding through the patulous duodenal papilla, which is bulging (arrows). (f) Photograph of the resected pancreas shows the dilated main duct (*) opened. A flat elongated tumor (hyperplasia and borderline malignancy) with a rough surface (arrows), 8 cm long and 1 cm wide, covers a wide area of the dilated main duct in the region of the pancreas body and tail. At microscopic study (not shown), focal areas of malignant change with stromal invasion were identified.
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Figure 9e. IPMT of borderline malignancy and focal carcinomatous change, main duct type, in a 37-year-old woman. (a-c) US (a), CT (b), and MRCP (2,317.8/185.8) (c) images show the markedly dilated main pancreatic duct. No mass or mucus is demonstrated. (d) ERCP image shows the markedly dilated main pancreatic duct with elongated filling defects (straight arrows) and an ill-defined scalloped margin (curved arrows) representing intraductal mucus or tumor. (e) Duodenal endoscopic image shows thick mucus (*) protruding through the patulous duodenal papilla, which is bulging (arrows). (f) Photograph of the resected pancreas shows the dilated main duct (*) opened. A flat elongated tumor (hyperplasia and borderline malignancy) with a rough surface (arrows), 8 cm long and 1 cm wide, covers a wide area of the dilated main duct in the region of the pancreas body and tail. At microscopic study (not shown), focal areas of malignant change with stromal invasion were identified.
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Figure 9f. IPMT of borderline malignancy and focal carcinomatous change, main duct type, in a 37-year-old woman. (a-c) US (a), CT (b), and MRCP (2,317.8/185.8) (c) images show the markedly dilated main pancreatic duct. No mass or mucus is demonstrated. (d) ERCP image shows the markedly dilated main pancreatic duct with elongated filling defects (straight arrows) and an ill-defined scalloped margin (curved arrows) representing intraductal mucus or tumor. (e) Duodenal endoscopic image shows thick mucus (*) protruding through the patulous duodenal papilla, which is bulging (arrows). (f) Photograph of the resected pancreas shows the dilated main duct (*) opened. A flat elongated tumor (hyperplasia and borderline malignancy) with a rough surface (arrows), 8 cm long and 1 cm wide, covers a wide area of the dilated main duct in the region of the pancreas body and tail. At microscopic study (not shown), focal areas of malignant change with stromal invasion were identified.
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Figure 10a. Intraductal papillary mucinous adenocarcinoma, main duct type, in a 55-year-old man. (a, b) CT (a) and T1-weighted MR (500/15) (b) images show the markedly dilated tortuous main pancreatic duct. Mucus or tumor is not depicted. (c) Intraoperative pancreatographic image shows the markedly dilated pancreatic duct containing large filling defects, which represent thick mucous plugs.
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Figure 10b. Intraductal papillary mucinous adenocarcinoma, main duct type, in a 55-year-old man. (a, b) CT (a) and T1-weighted MR (500/15) (b) images show the markedly dilated tortuous main pancreatic duct. Mucus or tumor is not depicted. (c) Intraoperative pancreatographic image shows the markedly dilated pancreatic duct containing large filling defects, which represent thick mucous plugs.
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Figure 10c. Intraductal papillary mucinous adenocarcinoma, main duct type, in a 55-year-old man. (a, b) CT (a) and T1-weighted MR (500/15) (b) images show the markedly dilated tortuous main pancreatic duct. Mucus or tumor is not depicted. (c) Intraoperative pancreatographic image shows the markedly dilated pancreatic duct containing large filling defects, which represent thick mucous plugs.
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IPMT, Combined Type
In the combined type of IPMT, both branch ducts of the uncinate process and the main pancreatic ducts are involved (3) (Fig 11). In some patients, the branch ducts along the body and tail may also be involved, and many small branch ducts along the main pancreatic ducts are dilated (Fig 12).
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Figure 11a. Intraductal papillary mucinous adenocarcinoma, combined main duct and branch duct type, in a 75-year-old man. (a, b) CT images show the dilated main pancreatic duct (arrows) and clustered cystic lesions in the uncinate process. (c) ERCP image shows dilated branch ducts (arrows) and the main pancreatic duct. Note severe stenosis of the distal common bile duct due to invasion of tumor.
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Figure 11b. Intraductal papillary mucinous adenocarcinoma, combined main duct and branch duct type, in a 75-year-old man. (a, b) CT images show the dilated main pancreatic duct (arrows) and clustered cystic lesions in the uncinate process. (c) ERCP image shows dilated branch ducts (arrows) and the main pancreatic duct. Note severe stenosis of the distal common bile duct due to invasion of tumor.
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Figure 11c. Intraductal papillary mucinous adenocarcinoma, combined main duct and branch duct type, in a 75-year-old man. (a, b) CT images show the dilated main pancreatic duct (arrows) and clustered cystic lesions in the uncinate process. (c) ERCP image shows dilated branch ducts (arrows) and the main pancreatic duct. Note severe stenosis of the distal common bile duct due to invasion of tumor.
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Figure 12a. Intraductal papillary mucinous adenoma, combined main duct and branch duct type, in a 67-year-old man. (a, b) CT (a) and MRCP (666.7/108.0) (b) images show marked dilatation of the main pancreatic duct ( in a) and mild dilatation of the side branch ducts (arrowheads in a) along the main pancreatic duct. (c) ERCP image shows inadequate opacification of the main pancreatic duct due to thick mucus. Few branch ducts in the uncinate process are depicted. Note the mucus (arrows) in the pancreatic duct. Thick mucus protruding through duodenal papilla was confirmed at endoscopy (not shown).
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Figure 12b. Intraductal papillary mucinous adenoma, combined main duct and branch duct type, in a 67-year-old man. (a, b) CT (a) and MRCP (666.7/108.0) (b) images show marked dilatation of the main pancreatic duct ( in a) and mild dilatation of the side branch ducts (arrowheads in a) along the main pancreatic duct. (c) ERCP image shows inadequate opacification of the main pancreatic duct due to thick mucus. Few branch ducts in the uncinate process are depicted. Note the mucus (arrows) in the pancreatic duct. Thick mucus protruding through duodenal papilla was confirmed at endoscopy (not shown).
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Figure 12c. Intraductal papillary mucinous adenoma, combined main duct and branch duct type, in a 67-year-old man. (a, b) CT (a) and MRCP (666.7/108.0) (b) images show marked dilatation of the main pancreatic duct ( in a) and mild dilatation of the side branch ducts (arrowheads in a) along the main pancreatic duct. (c) ERCP image shows inadequate opacification of the main pancreatic duct due to thick mucus. Few branch ducts in the uncinate process are depicted. Note the mucus (arrows) in the pancreatic duct. Thick mucus protruding through duodenal papilla was confirmed at endoscopy (not shown).
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Strengths and Weaknesses of Each Modality
At US, CT, or MRCP, the clustered cystically dilated branch ducts or dilated main pancreatic duct can be well demonstrated (1)–(5),(10),(20),(21), but demonstration of communication between the cystic lesion and the pancreatic duct is difficult or impossible (13). Thin-section helical CT may demonstrate direct communication between the cyst and the pancreatic ducts (20),(21). ERCP is the most effective modality to demonstrate the communication. Mucin and papillary tumor can be clearly demonstrated at ERCP as an elongated or nodular filling defect, but such tumors are difficult to demonstrate at US, CT, and MRCP (13) (Figs 5, 7, 9, 10). Distinction between mucin and papillary tumors is difficult when a filling defect is nodular (13),(20).
When a papillary tumor is small or flat, the tumor may not be depicted even with ERCP (Fig 9). The dilated main duct or branch ducts may not be seen at ERCP if viscous mucin or papillary growth of tumor affects the duct lumen and inhibits the adequate inflow of contrast material into the dilated branch ducts (3),(5),(13),(20) (Figs 4, 7, 12). In this regard, MRCP is the best modality for evaluation of the extent of disease (20) (Figs 7, 12). Small papillary tumors may not be depicted at thick-slab MRCP (Figs 5, 7, 10, 12).
Differential Diagnosis
Radiologic findings for chronic pancreatitis with pseudocyst (Figs 13, 14) or marked ductal dilation secondary to obstruction (Fig 15) may be similar to those for IPMT (3),(20). Differentiation of IPMT from pseudocyst necessitates demonstration of the intraductal filling defects of papillary tumor or a mucin glob (20). Chronic pancreatitis may be caused by IPMT, making differential diagnosis difficult clinically and radiologically (3) (Fig 6). Demonstration of the presence of mural nodules or intraductal mucin and herniation of the papilla into the duodenal lumen helps differentiate IPMT from chronic pancreatitis (17),(20),(21). In some patients with mucinous cystic neoplasm or microcystic adenoma (3),(20), there may be a communication between the cyst and pancreatic duct (Fig 16).
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Figure 13a. Chronic pancreatitis with pseudocyst in a 63-year-old man. (a-c) US (a), CT (b), and MRCP ( /185.8) (c) images show the multiple clustered small cystic lesions (arrows in a and b) in the uncinate process of the pancreas. The main pancreatic duct is dilated. (d) ERCP image shows complete obstruction of the pancreatic duct at the head (arrow). At surgery, chronic pancreatitis with pseudocysts was confirmed.
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Figure 13b. Chronic pancreatitis with pseudocyst in a 63-year-old man. (a-c) US (a), CT (b), and MRCP (/185.8) (c) images show the multiple clustered small cystic lesions (arrows in a and b) in the uncinate process of the pancreas. The main pancreatic duct is dilated. (d) ERCP image shows complete obstruction of the pancreatic duct at the head (arrow). At surgery, chronic pancreatitis with pseudocysts was confirmed.
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Figure 13c. Chronic pancreatitis with pseudocyst in a 63-year-old man. (a-c) US (a), CT (b), and MRCP (/185.8) (c) images show the multiple clustered small cystic lesions (arrows in a and b) in the uncinate process of the pancreas. The main pancreatic duct is dilated. (d) ERCP image shows complete obstruction of the pancreatic duct at the head (arrow). At surgery, chronic pancreatitis with pseudocysts was confirmed.
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Figure 13d. Chronic pancreatitis with pseudocyst in a 63-year-old man. (a-c) US (a), CT (b), and MRCP (/185.8) (c) images show the multiple clustered small cystic lesions (arrows in a and b) in the uncinate process of the pancreas. The main pancreatic duct is dilated. (d) ERCP image shows complete obstruction of the pancreatic duct at the head (arrow). At surgery, chronic pancreatitis with pseudocysts was confirmed.
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Figure 14a. Chronic pancreatitis with pseudocysts in the body of the pancreas in a 36-year-old woman. (a) CT image shows small clustered cysts in the pancreas body. (b) ERCP image shows communicating tiny cystic lesions in the body (arrows). Note normal pancreatic duct at the head and tail of the pancreas. (c) Photograph of the resected specimen shows chronic pancreatitis with fibrosis and multiple hemorrhagic pseudocysts (arrows). * = hemorrhage in the fat tissue of the splenic hilum.
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Figure 14b. Chronic pancreatitis with pseudocysts in the body of the pancreas in a 36-year-old woman. (a) CT image shows small clustered cysts in the pancreas body. (b) ERCP image shows communicating tiny cystic lesions in the body (arrows). Note normal pancreatic duct at the head and tail of the pancreas. (c) Photograph of the resected specimen shows chronic pancreatitis with fibrosis and multiple hemorrhagic pseudocysts (arrows). * = hemorrhage in the fat tissue of the splenic hilum.
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Figure 14c. Chronic pancreatitis with pseudocysts in the body of the pancreas in a 36-year-old woman. (a) CT image shows small clustered cysts in the pancreas body. (b) ERCP image shows communicating tiny cystic lesions in the body (arrows). Note normal pancreatic duct at the head and tail of the pancreas. (c) Photograph of the resected specimen shows chronic pancreatitis with fibrosis and multiple hemorrhagic pseudocysts (arrows). * = hemorrhage in the fat tissue of the splenic hilum.
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Figure 15a. Chronic pancreatitis with obstruction of the main pancreatic duct (retention cyst) in a 63-year-old woman. (a, b) US (a) and CT (b) images show a markedly dilated main pancreatic duct with severe atrophy of the pancreas. (c) ERCP image shows complete obstruction of the pancreatic duct at the neck (arrow). The distal pancreatic duct in the head is normal. (d) Photograph of the resected pancreas shows severe tubular dilatation of the main pancreatic duct owing to complete obstruction.
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Figure 15b. Chronic pancreatitis with obstruction of the main pancreatic duct (retention cyst) in a 63-year-old woman. (a, b) US (a) and CT (b) images show a markedly dilated main pancreatic duct with severe atrophy of the pancreas. (c) ERCP image shows complete obstruction of the pancreatic duct at the neck (arrow). The distal pancreatic duct in the head is normal. (d) Photograph of the resected pancreas shows severe tubular dilatation of the main pancreatic duct owing to complete obstruction.
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Figure 15c. Chronic pancreatitis with obstruction of the main pancreatic duct (retention cyst) in a 63-year-old woman. (a, b) US (a) and CT (b) images show a markedly dilated main pancreatic duct with severe atrophy of the pancreas. (c) ERCP image shows complete obstruction of the pancreatic duct at the neck (arrow). The distal pancreatic duct in the head is normal. (d) Photograph of the resected pancreas shows severe tubular dilatation of the main pancreatic duct owing to complete obstruction.
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Figure 15d. Chronic pancreatitis with obstruction of the main pancreatic duct (retention cyst) in a 63-year-old woman. (a, b) US (a) and CT (b) images show a markedly dilated main pancreatic duct with severe atrophy of the pancreas. (c) ERCP image shows complete obstruction of the pancreatic duct at the neck (arrow). The distal pancreatic duct in the head is normal. (d) Photograph of the resected pancreas shows severe tubular dilatation of the main pancreatic duct owing to complete obstruction.
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Figure 16a. Mucinous cystic neoplasm communicating with the main pancreatic duct in a 57-year-old woman. (a) CT image shows a small oval cystic lesion (arrow) in the neck of the pancreas. (b) ERCP image shows clustered cystic lesions in the neck portion that communicate with the main pancreatic duct. A small filling defect (arrow) is seen in the cystically dilated space. Note the normal diameter of the main pancreatic duct. (c) Photograph of the resected specimen shows a clustered cystic lesion in the neck of the pancreas that communicates with the main pancreatic duct. Microscopic study (not shown) revealed mucinous cystic neoplasm.
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Figure 16b. Mucinous cystic neoplasm communicating with the main pancreatic duct in a 57-year-old woman. (a) CT image shows a small oval cystic lesion (arrow) in the neck of the pancreas. (b) ERCP image shows clustered cystic lesions in the neck portion that communicate with the main pancreatic duct. A small filling defect (arrow) is seen in the cystically dilated space. Note the normal diameter of the main pancreatic duct. (c) Photograph of the resected specimen shows a clustered cystic lesion in the neck of the pancreas that communicates with the main pancreatic duct. Microscopic study (not shown) revealed mucinous cystic neoplasm.
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Figure 16c. Mucinous cystic neoplasm communicating with the main pancreatic duct in a 57-year-old woman. (a) CT image shows a small oval cystic lesion (arrow) in the neck of the pancreas. (b) ERCP image shows clustered cystic lesions in the neck portion that communicate with the main pancreatic duct. A small filling defect (arrow) is seen in the cystically dilated space. Note the normal diameter of the main pancreatic duct. (c) Photograph of the resected specimen shows a clustered cystic lesion in the neck of the pancreas that communicates with the main pancreatic duct. Microscopic study (not shown) revealed mucinous cystic neoplasm.
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Pathologically, mucinous cystic neoplasm is a large single uniloculated or multiloculated round or oval cystic tumor, whereas IPMT is basically dilatation of the main pancreatic duct or branch ducts due to excessive mucin production and disturbance in drainage. The gross shape of a cystic lesion in a mucinous cystic neoplasm is a globular mass possessing septa, whereas the gross shape of a cystic lesion in branch duct type IPMT is a grapelike clustered or lobulated cystic lesion. The main pancreatic duct in IPMT is dilated due to excessive mucin, but the main pancreatic duct in mucinous cystic neoplasm is not dilated even though there may be a communication between the pancreatic duct and cystic tumor.
Histologically, smooth muscle components are seen in the wall of the cyst in IPMT; however, ovarian-type stroma in epithelial stroma and fibrosis in the wall of the cyst (22) are seen in mucinous cystic neoplasm. Branch type IPMT occurs mainly in the head and uncinate process in elderly men, but mucinous cystic neoplasm commonly occurs in the body and tail of the pancreas in middle-aged women.
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Conclusions
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Results at noninvasive imaging studies such as US, CT, and MRCP can suggest IPMT on the basis of characteristic grapelike multicystic dilata-tion of the branch ducts in the uncinate process (branch type) or diffuse dilatation of the main pancreatic duct (main duct type), intraductal papillary tumors or mucus, and papilla bulging into the duodenum.
ERCP is the imaging modality of choice for the diagnosis on the basis of a communication between the dilated branch ducts and main pancreatic duct, as well as intraductal mucus or papillary tumor. In addition at duodenal endoscopy at the ti
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Abstract
Introduction
