Pancreatic Imaging Mimics - Ajr

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AJR:199 , August 2012 301

Pancreatic Imaging Mimics:Part 1, Imaging Mimics ofPancreatic Adenocarcinoma

Fergus V. Coakley1

Katryana Hanley-Knutson

John Mongan

Ramon Barajas

Matthew Bucknor

Aliya Qayyum

Coakley FV, Hanley-Knutson K, Mongan J, BarajasR, Bucknor M, Qayyum A

1All authors: Department o Radiology, University o

Caliornia San Francisco, Box 0628, M-372, 5 05Parnassus Ave, San Francisco, CA 94143 -0628 .

Address correspondence to F. V. Coakley

([email protected]).

Integrative Imaging Pictorial Essay

CME/SAM

This article is available or SAM/CME credit.

AJR2012; 199:301308

0361803X/12/1992301

American Roentgen Ray Society

Keywords: CT, imaging mimics, pancreatic

adenocarcinoma

DOI:10.2214/AJR.11.7907

Received September 6, 2011; accepted ater revision

February 15, 2012.

J. Mongan was supported by the National Institutes o

Biomedical Imaging and Bioengineering (T32 training

grant 1 T32 EB001631).

FOCUSON:

The purpose o this pictorial essay is to de-

scribe the imaging eatures o diseases that

may closely simulate pancreatic adenocarci-

noma, either radiologically or pathologically.

Neoplastic Mimics of Pancreatic

Adenocarcinoma

Neuroendocrine Tumors

Pancreatic neuroendocrine tumors account

or 5% o pancreatic tumors and may be asso-

ciated with von HippelLindau disease, neuro-

bromatosis-1, tuberous sclerosis, and mul-

tiple endocrine neoplasia type 1 syndrome.

The 5-year survival rate o 81% or pancreat-

ic neuroendocrine tumor [4] is signicantly

higher than that or pancreatic adenocarcino-

ma. On CT or MRI, pancreatic neuroendo-

crine tumor most commonly presents as a hy-

pervascular mass o variable size, best seen

on early arterial phase imaging. Unlike ad-

enocarcinoma, such tumors are oten well-

circumscribed and duct obstruction is un-

common [5] (Fig. 1). Duct obstruction, when

present, appears to be a eature o small well-

dierentiated serotonin-producing tumorsand may refect the local brogenic eect o

serotonin [6] (Fig. 2). They are oten larger

than adenocarcinomas, and IV tumor throm-

bus may be seen [7] (Fig. 3). Liver metas-

tases may be present; ndings that suggest

metastases rom neuroendocrine tumor rath-

er than adenocarcinoma include hypervas-

cularity, T2 hyperintensity, large size, intra-

lesional hemorrhage or necrosis, or positive

somatostatin receptor scintigraphy [8].

The accurate diagnosis o pancre-

atic adenocarcinoma is o criti-

cal importance, because the dis-

ease has a high mortality and its

treatment has substantial morbidity. Several

lines o evidence suggest that misdiagnosis,

either radiologically or pathologically, may

be relatively common. Published alse-nega-

tive rates or the pathologic misdiagnoses o

pancreatic adenocarcinoma range rom 1.6%

to 30% [1]. In a study o 25 patients who sur-

vived more than 5 years ater surgical resec-

tion or adenocarcinoma, 13 ailed to show

the typical pathologic characteristics o ade-

nocarcinoma on retrospective analysis [2].

In a series o 186 patients diagnosed with ad-

enocarcinoma who underwent resection, 12

had their diagnosis changed on urther path-

ologic review [2]. The American Cancer So-

ciety 5-year survival rate o 6% is discordant

with the much lower 5-year survival rate o

1.8% reported at Memorial Sloan-Kettering

Cancer Center, where the histologic diagno-

sis might be less subject to error [2, 3]. Anec-

dotally, we have encountered several patientssaid to have pancreatic adenocarcinoma on

the basis o erroneous radiologic or histo-

pathologic interpretations in whom atypical

imaging ndings were critical in establish-

ing the correct diagnosis. These consider-

ations suggest that the diagnosis o pancre-

atic cancer should be treated more like breast

cancer, with multidisciplinary involvement

o both radiologists and pathologists to re-

view cases o discordance or uncertainty.

OBJECTIVE. The purpose o this article is to describe the imaging eatures o diseases

that may closely simulate pancreatic adenocarcinoma, either radiologically or pathologically.

CONCLUSION. Neoplastic and infammatory diseases that can closely simulate pan-

creatic adenocarcinoma include neuroendocrine tumor, metastasis to the pancreas, lympho-

ma, groove pancreatitis, autoimmune pancreatitis, and ocal chronic pancreatitis. Atypical

imaging ndings that should suggest diagnoses other than adenocarcinoma include the ab-

sence o signicant duct dilatation, incidental detection, hypervascular ity, large size (> 5 cm),IV tumor thrombus, and intralesional ducts or cysts.

Coakley et al.Mimics o Pancreatic Adenocarcinoma

Integrative ImagingPictorial Essay

Pancreatic Imaging MimicsCMESAM


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302 AJR:199 , August 2012

Coakley et al.

Metastas is to the Pancreas

Metastases to the pancreas are relatively

uncommon, but the pancreas is a recognized

site o spread or both renal cell and lung can-

cer. Renal cell cancer is the single most com-

mon primary site in cases o metastases to the

pancreas, accounting or 30% o such lesions,

but they are usually hypervascular at CT andso are unlikely to be conused with pancre-

atic adenocarcinoma, which is generally hy-

povascular [9]. In addition, the diagnosis o

renal cell cancer is usually clear because o

changes related to prior nephrectomy or abla-

tion. Interestingly, in a recent MRI study, 50%

o renal cell carcinoma metastases to the pan-

creas were ound to be hypovascular on MRI

[10]. Lung cancer is the second most com-

mon primary site in cases o metastases to the

pancreas, accounting or 23% o such lesions,

and these tumors are requently hypovascular.

The nding o a hypovascular pancreatic head

mass without signicant biliary or pancreatic

duct dilatation should prompt consideration o

metastasis rom a primary bronchogenic car-

cinoma, and imaging o the chest may be use-

ul (Figs. 47). Metastases to the pancreas are

oten well circumscribed, another nding that

would be atypical or primary pancreatic ad-

enocarcinoma [10].

Pancreatic Lymphoma

Primary pancreatic lymphoma accounts

or less than 0.5% o pancreatic masses but

can potentially be cured, which is one rea-

son why it is important to diagnose correctly[11]. Primary pancreatic lymphoma is oten

bulky and encases the vasculature but does

not occlude it. Ductal dilatation and cystic

changes are rare [12] (Figs. 8 and 9).

Adenocarcinoma Arising in Intraductal

Papillary Mucinous Neoplasm

Adenocarcinoma arising in the setting o

intraductal papillary mucinous neoplasm may

not strictly constitute an imaging mimic o

de novo adenocarcinoma, because both rep-

resent primary epithelial malignancy o the

pancreas, but invasive cancer derived rom in-

traductal papillary mucinous neoplasm has a5-year survival rate o 34%, compared with

9% or standard adenocarcinoma [13], and

the radiologic appearances are distinctive. As

such, a brie description o the cross-section-

al ndings appears appropriate in this essay.

The natural history and requency o malig-

nant degeneration in intraductal papillary mu-

cinous neoplasms are not well established, but

it is known that cancer arises more requent-

ly in the main duct than in branch duct intra-

ductal papillary mucinous neoplasms [14]. A

main pancreatic duct diameter o over 6 mm,

a mural nodule greater than 3 mm in size, or

abnormal attenuation in the adjacent pancre-

atic parenchyma suggest malignancy in main

duct intraductal papillary mucinous neoplasm

(Figs. 10 and 11). Solid nodules, thick enhanc-ing walls or septations, a connection more than

1 cm in diameter between a dilated side branch

and the main pancreatic duct, or a tumor larger

than 3 cm suggest malignancy in branch duct

intraductal papillary mucinous neoplasm.

Inammatory Pseudotumors

Groove Pancreatitis

This condition is a orm o ocal chronic

pancreatitis that oten occurs in the groove

between the pancreatic head, common bile

duct, and the duodenum and is most common-

ly seen in middle-aged alcoholic men [15].

Groove pancreatitis presents as a poorly en-

hancing mass on CT or MRI. Unlike adeno-

carcinoma, ductal dilatation is uncommon, and

small intralesional ducts or cysts may be pres-

ent [16] and are oten best appreciated on MRI.

Imaging changes related to cystic dystrophy in

the duodenal wall, which likely refect a duo-

denal response to chronic or repeated infam-

mation, may be superimposed [17].

Autoimmune Pancreatit is

Autoimmune pancreatitis, also known as

lymphoplasmacytic (sclerosing) pancreatitis,

is oten associated with other autoimmuneconditions [18]. On CT, autoimmune pan-

creatitis presents with either diuse or ocal

enlargement that is isodense or slightly hy-

podense, most commonly in the head o the

pancreas. There may be irregular wall thick-

ening, narrowing o the main pancreatic duct,

peripancreatic stranding (halo sign), and en-

hancement o the gallbladder and common

bile duct [18] (Fig. 12). Extrapancreatic ab-

normalities associated with IgG4-related sys-

temic disease may be seen, including salivary

gland uptake on PET, retroperitoneal bro-

sis, periaortitis, infammatory renal pseudo-

tumors, and autoimmune cholangiopathy. Inaddition to these extrapancreatic eatures, the

lack o pancreatic duct dilatation is a key ea-

ture that distinguishes autoimmune pancreati-

tis rom adenocarcinoma.

Focal Chronic Pancreatitis

Focal chronic pancreatitis is most common-

ly related to alcohol abuse. On imaging, chron-

ic pancreatitis may present with pancreatic tail

atrophy and ductal dilatation (Fig. 13). Fo-

cal parenchymal sparing may mimic a mass.

Contrast-enhanced power Doppler ultra-

sound and diusion-weighted MRI may pro-

vide help in dierentiating the two entities,

with greater enhancement and apparent di-

usion coecient values seen in adenocarci-

noma [19, 20]. The visualization o an unob-structed main pancreatic duct penetrating a

pancreatic mass has been reported as a useul

sign that avors the diagnosis o an infam-

matory pseudotumor over pancreatic adeno-

carcinoma [21].

Conclusion

Neoplastic and infammatory diseases

that can simulate pancreatic adenocarcino-

ma include neuroendocrine tumor, metasta-

sis to the pancreas, lymphoma, groove pan-

creatitis, autoimmune pancreatitis, and ocal

chronic pancreatitis. Atypical ndings that

should suggest diagnoses other than adeno-

carcinoma include the absence o signicant

duct dilatation, incidental detection, hyper-

vascularity, large size (> 5 cm), venous inva-

sion, and intralesional ducts or cysts.

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8. Debray MP, Georoy O, Laissy JP, et al. Imaging

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9. Klein KA, Stephens DH, Welch TJ. CT character-

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Mimics of Pancreatic Adenocarcinoma

10. Takeuchi M, Matsuzaki K, Kubo H, Nishitani H.

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nance imaging o pancreatic cancer and mass-

orming chronic pancreatitis: preliminary results.

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11. Grimison PS, Chin MT, Harrison ML, Goldstein

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mours that are potentially curable without resec-

tiona retrospective review o our cases. BMC

Cancer2006; 6:117

12. Jayanthi V, Randhir J, Rajesh N. Problems in di-

agnosing lymphoma o the pancreas with com-

puted tomography: a case report.J Gastrointestin

Liver Dis 2007; 16:101103

13. Woo SM, Ryu JK, Lee SH, et al. Survival and

prognosis o invasive intraductal papillary muci-

nous neoplasms o the pancreas: comparison with

pancreatic ductal adenocarcinoma. Pancreas

2008; 36:5055

14. Pedrosa I, Boparai D. Imaging considerations in in-

traductal papillary mucinous neoplasms o the pan-

creas. World J Gastrointest Surg 2010; 2:324330

15. Itoh S, Yamakawa K, Shimamoto K, Endo T, Ish-

igaki T. CT ndings in groove pancreatitis: cor-

relation with histopathological ndings.J Comput

Assist Tomogr1994; 18:911915

16. Thomas H, Marriott P, Portmann B, Heaton N,

Rela M. Cystic dystrophy in heterotopic pancreas:

a rare indication or pancreaticoduodenectomy.

Hepatobiliary Pancreat Dis Int2009; 8:215217

17. Blasbalg R, Baroni RH, Costa DN, Machado

MCC. MRI eatures o groove pancreatitis. AJR

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18. Sahani DV, Saina ni NI, Deshpande V, Shaikh

MS, Frinkelberg DL, Fernandez-del Castillo C.

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22. Coak ley FV. Pitalls and pseudotumors in abdom-

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Society, 2012

Fig. 167-year-old man with vague abdominal discomort. Axial contrast-enhanced CT image shows hyper vascular mass (arrow) in head o pancreas.No biliary or pancreatic ductal dilatation was present (not shown). Resectionconrmed diagnosis o neuroendocrine tumor.

Fig. 245-year-old woman with intermittent nausea and vomiting. Axial curvedplanar reormatted image through pancreas shows isodense pancreatic mass(white arrows) with associated upstream pancreatic atrophy and ductal dilatation(black arrow). Tumor was positive at somatostatin scintigraphy, and resectionconrmed well-dierentiated pancreatic neuroendocrine tumor. Duct-obstructivepancreatic neuroendocrine tumor appears to refect serotonin production,causing local brosis and stricturing.

Fig. 377-year-old man with newly diagnosed myasthenia gravis. Axial contrast-enhanced CT image shows inltrative mass (arrow) in pancreatic tail, with tumor

thrombus extending into splenic vein. CT-guided biopsy o mass perormedat outside institution was interpreted as showing adenocarcinoma. Patientremained alive and well without treatment 18 months later. This clinical coursewas considered discordant with initial biopsy result. Biopsy was repeated at ourinstitution and revealed neuroendocrine tumor.


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A

Fig. 455-year-old woman with abdominal pain, weight loss, and 84 pack-year smoking history.A, Axial curved planar reormatted contrast-enhanced CT image shows ill-dened 3-cm mass (arrow) in pancreatic head. Absent biliary and minimal pancreatic ductaldilatation is atypical or pancreatic adenocarcinoma, suggesting alternative diagnosis such as lung cancer metastatic to pancreas. Chest CT was suggested.B, Axial contrast-enhanced chest CT image shows 2-cm spiculated mass (arrow) in let upper lobe. Biopsy conrmed diagnosis o nonsmall cell lung cancer.

B

A

Fig. 547-year-old woman who presented with epigastric pain and vomiting.A, Axial curved planar reormatted contrast-enhanced CT image shows 4-cm low-attenuating heterogeneous rim enhancing mass (white arrow) in junction o head andbody o pancreas. Additional lesions are present in pancreatic tail (verticalblack arrow) and right paraspinal musculature (horizontalblack arrow). Pancreatic duct ismildly dilated.B, Coronal enhanced curved planar reormatted CT image shows absence o biliary dilatation. This should raise suspicion o diagnosis other than pancreaticadenocarcinoma. This patient was subsequently diagnosed with metastatic nonsmall cell lung cancer to pancreas. (Reprinted rom [22]).

B

A

Fig. 670-year-old man.A, Axial curved planar reormatted contrast-enhanced CT image shows 1.5-cmlow-attenuating pancreatic head mass (arrow) with minimal pancreatic ductaldilatation. Lack o marked ductal dilatation suggests diagnosis other thanadenocarcinoma.

(Fig. 6 continues on next page)


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C

Fig. 6 (continued)70-year-old man.B, Axial abdominal ultrasound image shows that pancreatic head mass (arrow) isechogenic.C, Axial used image rom 18F-FDG PET/CT scan shows pancreatic head mass isintensely FDG-avid.D, Axial image rom FDG PET scan shows intensely FDG-avid primary lung cancerand intramuscular metastasis. Diagnosis o metastatic small cell lung cancer wasconrmed histologically. (Reprinted rom [22]).

B

D

A

Fig. 750-year-old man with abdominal pain and 75 pack-year smoking history.A, Axial curved planar reormatted contrast-enhanced CT image shows that large 6-cm pancreatic head mass ( arrow) is not associated with biliary dilatation. Large sizeand lack o biliary duct dilatation suggests that pancreatic mass is not primary pancreatic adenocarcinoma.B, Axial CT image o chest shows large right perihilar mass, and diagnosis o small cell lung cancer was conrmed histopathologically.

B


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Fig. 850-year-old man 2 years ater liver transplant or hepatitis Brelated cirrhosis.A, Axial curved planar reormatted contrast-enhanced CT image. Low-density 5-cm pancreatic head mass (arrow) is not associated with biliary dilatation, makingadenocarcinoma less likely diagnosis. Fine-needle aspiration was done on mass and interpreted as pancreatic adenocarcinoma. Six cycles o chemotherapy wereadministered, and mass resolved. Surgical exploration and repeat biopsy showed no evidence o adenocarcinoma. According to atypical surgical and imaging ndings,nal presumptive clinical diagnosis o posttransplant lymphoprolierative disorder was made.B, Coronal CT image shows mass (arrow) is not causing biliary dilatation. (Reprinted rom [22]).

B

A

Fig. 968-year-old woman with recurrent epigastric pain, weight loss, and

elevated lipase levels.A, Axial contrast-enhanced CT image shows mass (arrow) in pancreatic headassociated with circumerential wall thickening o descending duodenum. Otherimages (not shown) showed absence o biliary dilatation. Initial radiologic diagnosiso pancreatic adenocarcinoma was suggested. Patient was reerred to ourinstitution or possible resection, where large size and lack o biliary dilatation wereconsidered to be atypical or pancreatic adenocarcinoma. Biopsy was perormedand revealed lymphoma.B, Axial T1-weighted gadolinium-enhanced at-saturated image shows mass(arrow) is hypovascular.C, Axial single-shot rapid acquisition with reocused echoes T2-weighted imageshows mass (arrow) is o intermediate T2 signal intensity.

(Fig. 9 continues on next page)

B

C


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Fig. 9 (continued)68-year-old woman with recurrent epigastric pain, weightloss, and elevated lipase levels.D, Transverse abdominal ultrasound image shows mass (arrow) isheterogeneously hypoechoic.

D

A

Fig. 1077-year-old man with painless jaundice.A, Axial contrast-enhanced CT image shows moderate biliary dilatation and gross pancreatic duct dilatation ( arrow). Latter suggests main duct intraductal papillarymucinous neoplasm.B, Axial contrast-enhanced CT image shows large intracystic solid nodule (arrow) in dilated main pancreatic duct, consistent with malignancy arising in main ductintraductal papillary mucinous neoplasm. Diagnosis was conrmed at surgery. (Reprinted rom [22]).

B

Fig. 1156-y ear-old man with history o alcohol abuse. Axial curved planarreormatted contrast-enhanced CT image shows inltrative hypodense 3-cmmass (arrow) in pancreatic head. Fine-needle biopsy was initially interpretedas adenocarcinoma, and patient received our cycles o chemotherapy. Onote, mass was detected incidentally at CT peror med or ureteral colic.No signicant pancreatic or biliary ductal dilatation is present, and smallintralesional cysts are visible. At er recognition o these atypical imagingeatures, cytologic reinterpretation was requested and established naldiagnosis o groove pancreatitis.


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Fig. 1277-year-old man who presented with pneumonia and weight loss and was ound to have serum CA-19-9 level o 325 U/mL (normal, < 36 U/mL), promptingpresumptive clinical diagnosis o adenocarcinoma.A, Axial curved planar reormatted CT image shows diusely enlarged pancreas. However, no discrete mass is visible. Hypodense capsule or peripancreatic halo (areabetweenarrows) is present, and no biliary or pancreatic ductal dilatation is seen.B, Axial image rom 18F-FDG PET/CT scan shows diusely FDG-avid pancreas. Constellation o incidental detection, peripancreatic halo, absence o duct dilatation, anddiuse uptake o FDG on PET were considered highly suggestive o autoimmune pancreatitis. Steroids were administered and peripancreatic halo resolved on ollow-up,which was clinically considered as conrming diagnosis o autoimmune pancreatitis.

B

Fig. 1357-year-old man with recurrent epigastric pain and history o heavyalcohol use. On axial curved planar reormatted contrast-enhanced CT image,marked dilatation o pancreat ic duct can be traced to level o hypovascular mass(arrow) in pancreatic head. No biliary dilatation was seen. Biopsy o mass wasinterpreted as adenocarcinoma. Pat ient remained alive and well 3 years later.Specimen was reexamined and reinterpreted as showing infammatory cells only,and mass was ultimately considered most likely due to ocal chronic pancreatitis.

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