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Focal chronic pancreatitis mimicking intraductal papillary mucinous neoplasm of the pancreas
European Journal of Radiology Extra 66 (2008) e21–e24
Focal chronic pancreatitis mimicking intraductal papillary mucinous neoplasm of the pancreas Kumi Ozaki a,∗ , Shiro Miyayama b , Osamu Matsui a , Toshifumi Gabata a , Yasuyuki Asada c , Akira Takehara c , Yoh Zen d a
Department of Radiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8641, Japan b Department of Diagnostic Radiology, Fukuiken Saiseikai Hospital, 7-1 Funabashi, Wadanaka-cho, Fukui 918-8503, Japan c Department of Surgery, Fukuiken Saiseikai Hospital, 7-1 Funabashi, Wadanaka-cho, Fukui 918-8503, Japan d Department of Pathology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8641, Japan Received 12 January 2008; accepted 22 January 2008
Abstract A case of chronic pancreatitis localized in the pancreatic head mimicking intraductal papillary mucinous neoplasm (IPMN) is reported. The patient presented with obstructive jaundice caused by a pancreatic head mass. Imaging findings showed clustered small cystic lesions within the mass and delayed enhanced area adjacent the cystic lesions. A malignant IPMN was suspected but the surgical specimen showed focal chronic pancreatitis. © 2008 Elsevier Ireland Ltd. All rights reserved. Keywords: Chronic pancreatitis; Intraductal papillary mucinous neoplasm of the pancreas; Pancreatic cyst; Delayed enhancement
1. Introduction The branch duct-type of intraductal papillary mucinous neoplasm (IPMN) of the pancreas is thought to be less aggressive than the main duct-type or the combined type and sometimes can be followed up without surgical management [1]; however it has malignant potential, and the invasion to the adjacent tissue has infrequently been reported [2,3]. Therefore, the precise diagnosis of IPMN by imaging is clinically important. We encountered a case of obstructive jaundice caused by focal chronic pancreatitis with multiple small cystic lesions in the pancreatic head. The lesion mimicked a malignant IPMN invading the adjacent pancreatic parenchyma. In this report, we describe this case focusing on imaging and pathologic correlation. 2. Case report A 57-year-old man was referred to our hospital for a further examination of a pancreatic head lesion found by ultrasound and CT. He had occasionally experienced epigastralgia dur∗
Corresponding author. Tel.: +81 76 265 2323; fax: +81 76 234 4256. E-mail address: [email protected] (K. Ozaki).
1571-4675/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrex.2008.01.015
ing the previous month. He presented with jaundice and felt itchy for several days prior to his admission. He did not have a daily drinking habit. Laboratory analysis showed elevation of serum hepatobiliary enzyme levels and total bilirubin level (16.1 mg/dL [normal range, 0.2–1.0 mg/dL]). The serum levels of tumor markers were also slightly elevated (CEA/S was 4.0 U/mL [normal range <2.5 U/mL] and CA19-9 was 77 U/mL [normal range <37 U/mL]). The serum levels of pancreatic enzymes were normal. The white blood cell counts and the serum level of C-reactive protein were within the normal range. At first, upper gastrointestinal tract endoscopy was performed to manage jaundice. Endoscopy demonstrated the normal duodenal mucosa. The size of the papilla of Vater was normal and mucin secretion through the papilla was not observed. Endoscopic retrograde cholangiopancreatography (ERCP) showed severe stricture of the intrapancreatic common bile duct and mild and diffuse dilatation of the main pancreatic duct. An endoscopic naso-biliary drainage tube was subsequently placed. Cytology of the bile was class III. Unenhanced computed tomography (CT) showed a hypoattenuating mass lesion 3.5 cm in diameter in the pancreatic head (Fig. 1A). On arterial-dominant phase of dynamic CT, the lesion did not show early enhancement relative to the surrounding pancreas (Fig. 1B). Equilibrium-phase CT showed
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K. Ozaki et al. / European Journal of Radiology Extra 66 (2008) e21–e24
Fig. 1. (A) Unenhanced CT shows a hypoattenuating mass lesion approximately 3.5 cm in diameter in the pancreatic head (arrows). (B) On arterial-dominant phase, the lesion does not show early enhancement relative to the surrounding pancreas (arrow). (C) Equilibrium-phase CT shows delayed enhancement of the lesion (arrow).
delayed enhancement of the lesion. Multiple cystic lesions up to 1.5 cm in diameter were also demonstrated within the mass (Fig. 1C). On magnetic resonance (MR) images, the mass lesion showed inhomogenous hypointensity on T1-weighted images and hyperintenity on fat-suppressed T2-weighted images (Fig. 2A). Multiple small cystic lesions were also demonstrated in the mass. Within the largest cystic lesion, small hypointense nodules like mural nodules were demonstrated on T2-weighted images. On dynamic study, the mass lesion did not show early enhancement even in mural nodule-like lesions. The mass lesion showed delayed enhancement mainly around the cystic lesions but the mural nodule-like lesions showed no enhancement (Fig. 2B). Thickening and delayed enhancement of the intrapancreatic common bile duct wall adjacent to the mass lesion was also demonstrated. On MR cholangiopancreatography (MRCP), these cystic lesions seemed to connect with each other and appeared similar to cluster of dilated branch ducts (Fig. 2C). The main pancreatic duct was slightly dilated, although direct connection between these cystic lesions and the main pancreatic duct was not identified. From these imaging findings, a malignant tumor derived from IPMN was suspected and pancreaticoduodenectomy was performed. The pathological diagnosis was focal chronic pancreatitis with multiple retention cysts in the pancreatic head. Macroscopically, the mass lesion looked whitish and there were multiple small cystic lesions within it. The largest cystic
lesion displaced the common bile duct and contained granular proteins (Fig. 3A). It was speculated that these materials were demonstrated as mural nodules on MR images. Histologically, the infiltration of inflammatory cells and multiple retention cysts were seen in the lesion, and the diagnosis of focal chronic pancreatitis was established. Hyperplastic change and epithelial metaplasia were revealed in the dilated duct, but the columnar epithelia with mucinous hypertrophy and nuclear abnormalities were not seen (Fig. 3B). The etiology of chronic pancreatitis was unknown in this patient. 3. Discussion Chronic pancreatitis generally affects the entire pancreas and imaging diagnosis is not difficult. When it develops in a localized area, however, distinction from pancreatic ductal carcinoma is frequently difficult because the lesion is demonstrated as a hypovascular solid mass [4,5]. On the other hand, a diagnosis of the branch duct-type of IPMN is also not difficult because of its characteristic cystic form; however, it is important that focal chronic pancreatitis sometimes mimics IPMN because of marked cystic dilatation of the branch ducts. In the present case, imaging findings showed a mass lesion that occluded the common bile duct in the pancreatic head. Multiple small cystic lesions within the mass mimicked dilated branches of the pancreatic duct, especially on MRCP imaging,
K. Ozaki et al. / European Journal of Radiology Extra 66 (2008) e21–e24
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Fig. 2. (A) On a transverse T2-weighted fat-suppressed image, the mass lesion adjacent to cystic lesions shows inhomogenous hyperintensity (arrow). Within the maximal cystic lesion, a small hypointense area like mural nodules is demonstrated (arrowhead). (B) The mass lesion shows strong delayed enhancement mainly around the cystic lesions (arrowheads) and adjacent common bile duct (arrow) on a post-contrast T1-weighted image. (C) On MRCP, these cystic lesions seem to connect with each other and appear similar to clusters of dilated branch ducts (arrow). The main pancreatic duct is slightly dilated (arrowhead).
although it was unclear whether these cystic lesions connected with each other. In addition, the findings of mural nodule-like lesions in the largest cyst, and stenosis and wall thickening of the adjacent common bile duct let us to suspect a malignant tumor derived from IPMN. Cystic lesions in the pancreas are seen in several conditions or diseases. In neoplastic lesions, serous cystadenoma, mucinous cystic neoplasm, solid-pseudopapillary tumor, and IPMN are common [6]; however, these tumors except for IPMN could be distinguished from the present case considering various imaging findings, age, and sex. In non-neoplastic lesions, pseudocyst and retention cyst are common [6,7]. These lesions frequently accompany pancreatitis or ductal carcinoma. The precise diagnosis of pancreatic pseudocyst and retention cyst resulting from pancreatitis is not difficult when they are associated with typical findings of acute or chronic pancreatitis, such as edematous change of the pancreatic parenchyma, fluid collection surrounding the parenchyma, parenchymal calcifications or ductal stones, ductal dilatation, and atrophy of the parenchyma; however, the diagnosis may be difficult when pancreatitis occurs in a limited area without specific symptoms and laboratory findings.
Retrospectively, there are two keys to avoid misdiagnosis in the present case. First, small cystic lesions in the mass did not connect with not only each other but also the main pancreatic duct on all images except for MRCP. Second, strong delayed enhancement and thickness of cystic lesions wall and the common bile duct wall were observed on post-contrast T1-weighted MR images. Delayed enhancement is typically seen in tissue where fibrous tissue proliferates, such as pancreatic carcinoma or chronic pancreatitis [4,8], and the dilated branch duct wall of IPMN generally does not show delayed enhancement [1,9]. In addition, mural nodule-like lesions in the largest cyst showed no enhancement. On the basis of these findings, mural nodule-like lesions should be considered as non-viable tissue. In the present case, however, there was an area surrounding the cystic lesions that was demonstrated as hypoattenuating on unenhanced CT, hypointense on T1-weighted MR images, and hyperintense on T2-weighted MR images. We misdiagnosed this area as tumor infiltration derived from IPMN, corresponding with the focus of chronic pancreatitis in the surgical specimen. Tumor-associated focal pancreatitis has also been reported and makes it difficult to differentiate a tumor from chronic inflammation [4,5]. Furthermore, a lack of specific findings of pancreatitis on lab-
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K. Ozaki et al. / European Journal of Radiology Extra 66 (2008) e21–e24
In conclusion, chronic pancreatitis infrequently affects a small area, produces marked cystic dilatation of the branch ducts, and mimics a pancreatic tumor derived from IPMN. It is important to recognize this condition to avoid excessive treatment. References
Fig. 3. (A) Macroscopically, the mass lesion looks whitish and there are multiple small cystic lesions within it. The maximal cystic lesion displaces the common bile duct and contains granular proteins (arrow). (B) Histologically, infiltration of inflammatory cells and multiple retention cysts are seen in the lesion. Hyperplastic change and epithelial metaplasia are revealed in the dilated duct, but columnar epithelia with mucinous hypertrophy and nuclear abnormalities are not seen.
oratory tests may make it difficult to diagnose as focal chronic pancreatitis.
[1] Sai JK, Suyama M, Kubokawa Y, et al. Management of branch duct-type intraductal papillary mucinous tumor of the pancreas based on magnetic resonance imaging. Abdom Imaging 2003;28:694–9. [2] Yamaguchi K, Ohuchida J, Ohtsuka T, et al. Intraductal papillary-mucinous tumor of the pancreas concomitant with ductal carcinoma of the pancreas. Pancreatology 2002;2:484–90. [3] Yamada Y, Mori H, Matsumoto S, et al. Invasive carcinomas derived from intraductal papillary mucinous neoplasms of the pancreas: a longterm follow-up assessment with CT imaging. J Comput Assist Tomogr 2006;30:885–90. [4] Kim T, Murakami T, Takamura M, et al. Pancreatic mass due to chronic pancreatitis: correlation of CT and MR imaging features with pathologic findings. AJR Am J Roentgenol 2001;177:367–71. [5] Gabata T, Sanada J, Kobayashi S, et al. Tumor-associated focal chronic pancreatitis from invasion of the pancreatic duct by common bile duct carcinoma: radiologic–pathologic correlation. Abdom Imaging 2003;28: 378–80. [6] Kim YH, Saini S, Sahani D, et al. Imaging diagnosis of cystic pancreatic lesions: pseudocyst versus nonpseudocyst. Radiographics 2005;25: 671–85. [7] Demos TC, Posniak HV, Harmath C, et al. Cystic lesions of the pancreas. AJR Am J Roentgenol 2002;179:1375–88. [8] Johnson PT, Outwater EK. Pancreatic carcinoma versus chronic pancreatitis: dynamic MR imaging. Radiology 1999;212:213–8. [9] Procacci C, Megibow AJ, Carbognin G, et al. Intraductal papillary mucinous tumor of the pancreas: a pictorial essay. Radiographics 1999;19: 1447–63.
Focal chronic pancreatitis mimicking intraductal papillary mucinous neoplasm of the pancreas Kumi Ozaki a,∗ , Shiro Miyayama b , Osamu Matsui a , Toshifumi Gabata a , Yasuyuki Asada c , Akira Takehara c , Yoh Zen d a
Department of Radiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8641, Japan b Department of Diagnostic Radiology, Fukuiken Saiseikai Hospital, 7-1 Funabashi, Wadanaka-cho, Fukui 918-8503, Japan c Department of Surgery, Fukuiken Saiseikai Hospital, 7-1 Funabashi, Wadanaka-cho, Fukui 918-8503, Japan d Department of Pathology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8641, Japan Received 12 January 2008; accepted 22 January 2008
Abstract A case of chronic pancreatitis localized in the pancreatic head mimicking intraductal papillary mucinous neoplasm (IPMN) is reported. The patient presented with obstructive jaundice caused by a pancreatic head mass. Imaging findings showed clustered small cystic lesions within the mass and delayed enhanced area adjacent the cystic lesions. A malignant IPMN was suspected but the surgical specimen showed focal chronic pancreatitis. © 2008 Elsevier Ireland Ltd. All rights reserved. Keywords: Chronic pancreatitis; Intraductal papillary mucinous neoplasm of the pancreas; Pancreatic cyst; Delayed enhancement
1. Introduction The branch duct-type of intraductal papillary mucinous neoplasm (IPMN) of the pancreas is thought to be less aggressive than the main duct-type or the combined type and sometimes can be followed up without surgical management [1]; however it has malignant potential, and the invasion to the adjacent tissue has infrequently been reported [2,3]. Therefore, the precise diagnosis of IPMN by imaging is clinically important. We encountered a case of obstructive jaundice caused by focal chronic pancreatitis with multiple small cystic lesions in the pancreatic head. The lesion mimicked a malignant IPMN invading the adjacent pancreatic parenchyma. In this report, we describe this case focusing on imaging and pathologic correlation. 2. Case report A 57-year-old man was referred to our hospital for a further examination of a pancreatic head lesion found by ultrasound and CT. He had occasionally experienced epigastralgia dur∗
Corresponding author. Tel.: +81 76 265 2323; fax: +81 76 234 4256. E-mail address: [email protected] (K. Ozaki).
1571-4675/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrex.2008.01.015
ing the previous month. He presented with jaundice and felt itchy for several days prior to his admission. He did not have a daily drinking habit. Laboratory analysis showed elevation of serum hepatobiliary enzyme levels and total bilirubin level (16.1 mg/dL [normal range, 0.2–1.0 mg/dL]). The serum levels of tumor markers were also slightly elevated (CEA/S was 4.0 U/mL [normal range <2.5 U/mL] and CA19-9 was 77 U/mL [normal range <37 U/mL]). The serum levels of pancreatic enzymes were normal. The white blood cell counts and the serum level of C-reactive protein were within the normal range. At first, upper gastrointestinal tract endoscopy was performed to manage jaundice. Endoscopy demonstrated the normal duodenal mucosa. The size of the papilla of Vater was normal and mucin secretion through the papilla was not observed. Endoscopic retrograde cholangiopancreatography (ERCP) showed severe stricture of the intrapancreatic common bile duct and mild and diffuse dilatation of the main pancreatic duct. An endoscopic naso-biliary drainage tube was subsequently placed. Cytology of the bile was class III. Unenhanced computed tomography (CT) showed a hypoattenuating mass lesion 3.5 cm in diameter in the pancreatic head (Fig. 1A). On arterial-dominant phase of dynamic CT, the lesion did not show early enhancement relative to the surrounding pancreas (Fig. 1B). Equilibrium-phase CT showed
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K. Ozaki et al. / European Journal of Radiology Extra 66 (2008) e21–e24
Fig. 1. (A) Unenhanced CT shows a hypoattenuating mass lesion approximately 3.5 cm in diameter in the pancreatic head (arrows). (B) On arterial-dominant phase, the lesion does not show early enhancement relative to the surrounding pancreas (arrow). (C) Equilibrium-phase CT shows delayed enhancement of the lesion (arrow).
delayed enhancement of the lesion. Multiple cystic lesions up to 1.5 cm in diameter were also demonstrated within the mass (Fig. 1C). On magnetic resonance (MR) images, the mass lesion showed inhomogenous hypointensity on T1-weighted images and hyperintenity on fat-suppressed T2-weighted images (Fig. 2A). Multiple small cystic lesions were also demonstrated in the mass. Within the largest cystic lesion, small hypointense nodules like mural nodules were demonstrated on T2-weighted images. On dynamic study, the mass lesion did not show early enhancement even in mural nodule-like lesions. The mass lesion showed delayed enhancement mainly around the cystic lesions but the mural nodule-like lesions showed no enhancement (Fig. 2B). Thickening and delayed enhancement of the intrapancreatic common bile duct wall adjacent to the mass lesion was also demonstrated. On MR cholangiopancreatography (MRCP), these cystic lesions seemed to connect with each other and appeared similar to cluster of dilated branch ducts (Fig. 2C). The main pancreatic duct was slightly dilated, although direct connection between these cystic lesions and the main pancreatic duct was not identified. From these imaging findings, a malignant tumor derived from IPMN was suspected and pancreaticoduodenectomy was performed. The pathological diagnosis was focal chronic pancreatitis with multiple retention cysts in the pancreatic head. Macroscopically, the mass lesion looked whitish and there were multiple small cystic lesions within it. The largest cystic
lesion displaced the common bile duct and contained granular proteins (Fig. 3A). It was speculated that these materials were demonstrated as mural nodules on MR images. Histologically, the infiltration of inflammatory cells and multiple retention cysts were seen in the lesion, and the diagnosis of focal chronic pancreatitis was established. Hyperplastic change and epithelial metaplasia were revealed in the dilated duct, but the columnar epithelia with mucinous hypertrophy and nuclear abnormalities were not seen (Fig. 3B). The etiology of chronic pancreatitis was unknown in this patient. 3. Discussion Chronic pancreatitis generally affects the entire pancreas and imaging diagnosis is not difficult. When it develops in a localized area, however, distinction from pancreatic ductal carcinoma is frequently difficult because the lesion is demonstrated as a hypovascular solid mass [4,5]. On the other hand, a diagnosis of the branch duct-type of IPMN is also not difficult because of its characteristic cystic form; however, it is important that focal chronic pancreatitis sometimes mimics IPMN because of marked cystic dilatation of the branch ducts. In the present case, imaging findings showed a mass lesion that occluded the common bile duct in the pancreatic head. Multiple small cystic lesions within the mass mimicked dilated branches of the pancreatic duct, especially on MRCP imaging,
K. Ozaki et al. / European Journal of Radiology Extra 66 (2008) e21–e24
e23
Fig. 2. (A) On a transverse T2-weighted fat-suppressed image, the mass lesion adjacent to cystic lesions shows inhomogenous hyperintensity (arrow). Within the maximal cystic lesion, a small hypointense area like mural nodules is demonstrated (arrowhead). (B) The mass lesion shows strong delayed enhancement mainly around the cystic lesions (arrowheads) and adjacent common bile duct (arrow) on a post-contrast T1-weighted image. (C) On MRCP, these cystic lesions seem to connect with each other and appear similar to clusters of dilated branch ducts (arrow). The main pancreatic duct is slightly dilated (arrowhead).
although it was unclear whether these cystic lesions connected with each other. In addition, the findings of mural nodule-like lesions in the largest cyst, and stenosis and wall thickening of the adjacent common bile duct let us to suspect a malignant tumor derived from IPMN. Cystic lesions in the pancreas are seen in several conditions or diseases. In neoplastic lesions, serous cystadenoma, mucinous cystic neoplasm, solid-pseudopapillary tumor, and IPMN are common [6]; however, these tumors except for IPMN could be distinguished from the present case considering various imaging findings, age, and sex. In non-neoplastic lesions, pseudocyst and retention cyst are common [6,7]. These lesions frequently accompany pancreatitis or ductal carcinoma. The precise diagnosis of pancreatic pseudocyst and retention cyst resulting from pancreatitis is not difficult when they are associated with typical findings of acute or chronic pancreatitis, such as edematous change of the pancreatic parenchyma, fluid collection surrounding the parenchyma, parenchymal calcifications or ductal stones, ductal dilatation, and atrophy of the parenchyma; however, the diagnosis may be difficult when pancreatitis occurs in a limited area without specific symptoms and laboratory findings.
Retrospectively, there are two keys to avoid misdiagnosis in the present case. First, small cystic lesions in the mass did not connect with not only each other but also the main pancreatic duct on all images except for MRCP. Second, strong delayed enhancement and thickness of cystic lesions wall and the common bile duct wall were observed on post-contrast T1-weighted MR images. Delayed enhancement is typically seen in tissue where fibrous tissue proliferates, such as pancreatic carcinoma or chronic pancreatitis [4,8], and the dilated branch duct wall of IPMN generally does not show delayed enhancement [1,9]. In addition, mural nodule-like lesions in the largest cyst showed no enhancement. On the basis of these findings, mural nodule-like lesions should be considered as non-viable tissue. In the present case, however, there was an area surrounding the cystic lesions that was demonstrated as hypoattenuating on unenhanced CT, hypointense on T1-weighted MR images, and hyperintense on T2-weighted MR images. We misdiagnosed this area as tumor infiltration derived from IPMN, corresponding with the focus of chronic pancreatitis in the surgical specimen. Tumor-associated focal pancreatitis has also been reported and makes it difficult to differentiate a tumor from chronic inflammation [4,5]. Furthermore, a lack of specific findings of pancreatitis on lab-
e24
K. Ozaki et al. / European Journal of Radiology Extra 66 (2008) e21–e24
In conclusion, chronic pancreatitis infrequently affects a small area, produces marked cystic dilatation of the branch ducts, and mimics a pancreatic tumor derived from IPMN. It is important to recognize this condition to avoid excessive treatment. References
Fig. 3. (A) Macroscopically, the mass lesion looks whitish and there are multiple small cystic lesions within it. The maximal cystic lesion displaces the common bile duct and contains granular proteins (arrow). (B) Histologically, infiltration of inflammatory cells and multiple retention cysts are seen in the lesion. Hyperplastic change and epithelial metaplasia are revealed in the dilated duct, but columnar epithelia with mucinous hypertrophy and nuclear abnormalities are not seen.
oratory tests may make it difficult to diagnose as focal chronic pancreatitis.
[1] Sai JK, Suyama M, Kubokawa Y, et al. Management of branch duct-type intraductal papillary mucinous tumor of the pancreas based on magnetic resonance imaging. Abdom Imaging 2003;28:694–9. [2] Yamaguchi K, Ohuchida J, Ohtsuka T, et al. Intraductal papillary-mucinous tumor of the pancreas concomitant with ductal carcinoma of the pancreas. Pancreatology 2002;2:484–90. [3] Yamada Y, Mori H, Matsumoto S, et al. Invasive carcinomas derived from intraductal papillary mucinous neoplasms of the pancreas: a longterm follow-up assessment with CT imaging. J Comput Assist Tomogr 2006;30:885–90. [4] Kim T, Murakami T, Takamura M, et al. Pancreatic mass due to chronic pancreatitis: correlation of CT and MR imaging features with pathologic findings. AJR Am J Roentgenol 2001;177:367–71. [5] Gabata T, Sanada J, Kobayashi S, et al. Tumor-associated focal chronic pancreatitis from invasion of the pancreatic duct by common bile duct carcinoma: radiologic–pathologic correlation. Abdom Imaging 2003;28: 378–80. [6] Kim YH, Saini S, Sahani D, et al. Imaging diagnosis of cystic pancreatic lesions: pseudocyst versus nonpseudocyst. Radiographics 2005;25: 671–85. [7] Demos TC, Posniak HV, Harmath C, et al. Cystic lesions of the pancreas. AJR Am J Roentgenol 2002;179:1375–88. [8] Johnson PT, Outwater EK. Pancreatic carcinoma versus chronic pancreatitis: dynamic MR imaging. Radiology 1999;212:213–8. [9] Procacci C, Megibow AJ, Carbognin G, et al. Intraductal papillary mucinous tumor of the pancreas: a pictorial essay. Radiographics 1999;19: 1447–63.