Imaging mimics of pancreatic ductaladenocarcinoma

Namita S. Gandhi,1 Myra K. Feldman,1 Ott Le,2 Gareth Morris-Stiff3

1Imaging Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA2Department of Diagnostic Radiology, University of Texas MD Anderson Cancer Center, Houston, TX, USA3Digestive Disease Institute, Cleveland Clinic, Cleveland, OH, USA

Abstract

Pancreatic ductal adenocarcinoma is the most commonprimary malignancy of the pancreas. The classic imagingfeatures are a hypovascular mass with proximal ductaldilatation. Different pancreatic pathologies can mimicthe imaging appearance of carcinoma including othertumors involving the pancreas (pancreatic neuroen-docrine tumors, lymphoma, metastasis, and rare tumorslike pancreatic acinar cell carcinoma and solid pseu-dopapillary tumors), inflammatory processes (chronicpancreatitis and autoimmune pancreatitis), and ana-tomic variants (annular pancreas). Differentiation be-tween these entities can sometimes be challenging due tooverlap of imaging features. The purpose of this article isto describe the common entities that can mimic pancre-atic cancer on imaging with illustrative examples and tosuggest features that can help in differentiation of theseentities.

Key words: Pancreas—Ductaladenocarcinoma—Mimics—Pancreatitis—Metastasis

Pancreatic ductal adenocarcinoma (PDAC) is the mostcommon primary malignancy of the pancreas, seen inabout 80% of the cases [1]. Classic features of PDAC onimaging are a hypovascular mass with upstream pan-creatic duct dilatation (Fig. 1). Most common location isin the head and there may be associated CBD dilatation.There may be associated encasement of vessels andlymphadenopathy. A dual-phase CT (late arterial andportal venous phase) or multiphasic MRI are the imag-ing modalities of choice and helps not only in diagnosis,but also in staging and preoperative planning for thepancreatic tumors [2]. The only curative therapy for

PDAC is surgery [3]. Pancreaticoduodenectomy is themost common surgery for pancreatic head carcinomas.Incidence of benign disease at pancreatiduodenectomyranges from approximately 6% to 10% [4, 5]. The dif-ferent pathologies that mimic PDAC in clinical presen-tation and on imaging include tumors other than PDAC,inflammatory processes, and anatomic variants.

The purpose of this pictorial assay is to describe theimaging features of diseases that can closely mimicPDAC on imaging and to suggest some key diagnosticfeatures to help differentiate these processes.

Neoplastic mimics of PDAC

Pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are aheterogeneous group of potentially malignant tumorsestimated to make up 10% of pancreatic cancers byprevalence [6]. PNET can be non-functioning or func-tioning. While PNET most commonly occurs sporadi-cally, the lesions can arise in conjunction with geneticsyndromes including multiple endocrine neoplasia(MEN) type 1, Tuberous Sclerosis, Von Hippel–Lindau,and neurofibromatosis type 1. Lesions have been classi-cally described as being solid, well-circumscribed masseswhich are hypervascular compared to the backgroundpancreas on the arterial phase of contrast enhancementand either hyper or isoattenuating to the pancreas on theportal venous phase of contrast enhancement [7]. Largertumors can be heterogeneous with areas of cystic change,calcifications, and heterogeneous enhancement [8]. Sev-eral studies have shown that between 41% and 49% ofPNET tumors may not show arterial phase hyperen-hancement [9]. These non-hypervascular PNETS may beconfused for PDAC on imaging studies. For non-hy-pervascular tumors, a well-circumscribed margin,homogeneous enhancement, and less severe upstream

Correspondence to: Namita S. Gandhi; email: gandhin@ccf.org

ª Springer Science+Business Media, LLC 2017

AbdominalRadiology

Abdom Radiol (2017)

DOI: 10.1007/s00261-017-1330-1

pancreatic duct dilation are imaging features that maysuggest PNET rather than PDAC [10] (Figs. 2, 3).

Metastasis

Metastatic disease to the pancreas is uncommon, makingup only 2%–5% of all pancreatic malignancies [11]. Themost common primary malignancy to metastasize to thepancreas is renal cell carcinoma (RCC). Other malig-nancies to metastasize to pancreas include breast, lung,melanoma, gastrointestinal tract tumors, thyroid, andosteosarcoma. Pancreatic metastasis may be single,multiple, or involve the pancreas diffusely. The appear-ance of metastatic disease to the pancreas is variable anddepends on the primary malignancy. RCC are hyper-

vascular tumors and metastases from RCC are alsohypervascular and thus unlikely to be mistaken forPDAC [12]. Hypoenhancing metastases from hypovas-cular primary tumors can mimic PDAC. Some metastaticlesions can invade the ductal epithelium, causingobstruction of the pancreatic duct and an imaging pic-ture identical to PDAC [13]. Clinical history of a knownprimary tumor and identification of additional sites ofmetastatic disease outside of the pancreas are importantdiagnostic clues. Tissue sampling may be necessary toconfirm the diagnosis (Fig. 4).

Lymphoma

Lymphomatous involvement of the pancreas can beclassified as either primary or secondary. Primary pan-creatic lymphoma (PPL) is a rare extra-nodal subtype of

Fig. 1. A 47-year-old man with painless jaundice. A Axialcontrast-enhanced (CE) CT image shows a hypoenhancingpancreatic head mass (white arrows) abutting the SMV.B Axial CECT image shows that the upstream pancreatic ductis dilated and the pancreas is atrophic (white dashed arrows).

Fig. 2. A 59-year-old woman with a 2-month history ofintermittent epigastric and LUQ pain. A Axial CECT shows asolid, well-circumscribed, hypoenhancing pancreatic tail mass(white arrows). PDAC could have an identical appearance.B Axial T1 CE MR of the same lesion performed during thevenous phase of contrast enhancement shows that the lesionis centrally hypoenhancing with a hyperenhancing rim (da-shed white arrows). Subsequent resection confirmed this le-sion to be a PNET.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

lymphoma, most often of non-Hodgkin B-cell type.Criteria for the diagnosis of primary pancreatic lym-phoma, originally established by Dawson et al., includelymphoma arising as a mass within the pancreas andperipancreatic lymph nodes with no liver or spleeninvolvement, no superficial or mediastinal lym-phadenopathy, and a normal leukocyte count [14, 15].Secondary pancreatic lymphoma occurs when the pan-creas is involved by lymphoma extending from adjacentlymph nodes or organs. This form is more common, andthe pancreas is estimated to be involved in up to 30% ofcases of Non-Hodgkins lymphoma [15].

On imaging, pancreatic lymphoma can present in twodistinct morphologic forms; a focal mass-like form and adiffuse, infiltrating form [16, 17]. The diffuse, infiltratingform of pancreatic lymphoma could be confused withpancreatitis and the focal mass-like form can mimicPDAC. The mass-like form of PPL most commonly oc-

Fig. 4. A 64-year-old man with known medullary thyroidcarcinoma. A Axial CECT shows an ill-defined hypoattenu-ating lesion within the pancreatic tail (white arrow). B AxialCECT in the same patient shows a low attenuation liver lesion(black arrow) compatible with hepatic metastatic disease.

Fig. 3. A 51-year-old woman with jaundice. A CoronalHASTE MRI image shows mildly dilated intrahepatic bile ductsand a dilated common bile duct (CBD) (solid white arrow).There is abrupt cut-off of the CBD by a mildly T2 hyperintensepancreatic head mass (dashed white arrow). B Axial diffusion-weighted image (DWI) shows restriction in the lesion (blockarrowhead). C Axial post-contrast T1 image shows a hypoen-hancing mass (curved arrow). The upstream pancreatic ductwasnot dilated.SubsequentEUS-guided fineneedle aspiration(FNA) confirmed poorly differentiated PNET.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

curs in the pancreatic head [18]. Like PDAC, the focalform of pancreatic lymphoma will typically showhypoenhancement compared to the background pan-creas [16].

As is true for lymphoma in other locations, pancreaticlymphoma may encase structures without causingobstruction or occlusion. Studies evaluating the pancre-atic duct by ERCP and CT showed the pancreatic duct tobe normal, displaced, or narrowed in association withpancreatic lymphoma and only rarely moderate to se-verely narrowed [16, 17]. Identification of encasedstructures without obstruction or occlusion can be usedas a key imaging feature to suggest the diagnosis oflymphoma over PDAC (Fig. 5). Lymphoma may be seenin association with lymphadenopathy below the renalveins. Untreated pancreatic lymphoma will not containcalcifications. Necrosis has not been described withpancreatic lymphoma [16]. Tissue sampling is necessaryto confirm diagnosis.

Solid pseudopapillary tumor

Solid pseudopapillary tumors (SPT) are rare, indolentpancreatic tumors with malignant potential. The diag-nosis can often be made presumptively due to charac-teristic imaging features and demographic features asthese lesions occur primarily in young women (secondthrough fourth decade) [19]. On imaging, SPT lesions areencapsulated. They are typically large when first dis-covered, with a reported mean diameter of 9 cm at thetime of diagnosis [20]. While small lesions may be entirelysolid, lesions larger than 3 cm are characterized by avariable mix of solid and cystic components. On CT, the

solid components are lower attenuation than the pan-creas on unenhanced images and most lesions showhypoenhancement on both the pancreatic and venousphase of contrast enhancement [21]. Hemorrhagic com-ponents are typically present within these tumors andthis can serve as a key imaging feature to suggest thediagnosis. MR is particularly well-suited for demon-stration of hemorrhagic components within these lesions[22]. Calcifications are seen in more than half of casesand are typically peripheral [21]. Although the lesions areoften large, associated duct obstruction is rare [23].Infiltrative growth pattern and vascular invasion are alsouncommon features of these tumors. Metastatic diseaseis rare and when present, has been reported in the liver[19] (Fig 6).

Fig. 6. A 21-year-old woman with abdominal pain. A AxialCECT shows a well-circumscribed, heterogeneous, hypoen-hancing pancreatic head mass (white arrows). B The up-stream pancreatic duct is not dilated and there is no upstreampancreatic atrophy. Subsequent surgical resection confirmedthis lesion to be a solid pseudopapillary tumor.

Fig. 5. A 75-year-old man with painless jaundice. A AxialCECT performed during the pancreatic phase of contrastenhancement shows a subtle hypoenhancing lesion in thepancreatic head (white solid arrows). This lesion encases theGDA which remains patent (dashed arrow). Subsequentbiopsy showed primary pancreatic lymphoma.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

Pancreatic acinar cell carcinoma

Pancreatic acinar cell carcinomas (PACC) are rare neo-plasms that make up approximately 1% of all exocrinepancreatic tumors [24]. The prognosis for PACC is poorthough slightly better than PDAC. Several studies haveshown that PACC tend to be large with average lesionsize ranging in the literature from 6 to 10 cm [24, 25].Unlike PDAC, most PACC lesions are well-marginatedand may show a well-defined capsule [24–26]. Tumorsare most commonly solid with cystic components re-ported in larger lesions [24]. Like PDAC, PACC lesionstend to be hypovascular compared to normal pancreatictissue on both the arterial and portal venous phase ofcontrast enhancement [25]. Associated pancreatic or bileduct obstruction has been reported in a minority of cases.

Metastatic disease is commonly present at the time ofinitial diagnosis [27]. Key imaging features that maysuggest PACC rather than PDAC include large sizewithout duct obstruction and well-defined borders(Fig. 7).

Serous cystadenoma

Majority of serous cystadenomas (SCA) have the classicpolycystic appearance and do not pose a diagnostic di-lemma with PDAC. The less common honeycomb pat-tern of SCA has numerous subcentimeter cysts which canappear as hypoenhancement on CT. This can pose a

Fig. 7. A 65-year-old man with history of vague right upperabdominal pain for several months. A Coronal pancreaticphase CECT shows a well-circumscribed, heterogeneouspancreatic head mass (white arrows). B Axial pancreaticphase CECT image from the same patient shows normalcaliber pancreatic duct upstream from the mass (curved ar-row). Surgical resection confirmed acinar cell carcinoma.

Fig. 8. A 56-year-old woman with an incidentally discoveredpancreatic mass noted on CT performed for work-up of arenal cyst. A Axial CECT and B coronal CECT images showsa low attenuation pancreatic head mass (white arrows). EUS-guided biopsy was inconclusive. Surgical resection confirmedserous cystadenoma.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

diagnostic dilemma with PDAC. There is usually noupstream ductal dilatation and there is a sharp interfacewith adjacent vasculature [28] (Fig. 8).

Other rare pancreatic tumors may also mimic PDACincluding solid serous tumors, hamartomas, and solitaryfibrous tumors [29–31] (Fig. 9).

Inflammatory mimics of PDAC

Some common inflammatory conditions of the pancreaslike chronic pancreatitis, focal autoimmune pancreatitis,and groove pancreatitis can present as a focal mass-likeprocess which can be mistaken for PDAC. It is importantthat the radiologists be familiar with these entities andreport that the process might be due to a non-neoplasticetiology. This can potentially minimize unnecessaryinvasive testing and pancreatic resections.

Chronic pancreatitis

Chronic pancreatitis (CP) is characterized by recurrentepisodes of inflammation which leads to glandularatrophy and fibrosis. Diffuse form is more common andhas a diagnostic appearance with parenchymal atrophy,ductal dilatation with prominent side branches, andductal calcifications. Focal pancreatitis can lead to focalatrophy or enlargement of the gland simulating PDACon imaging. On imaging, it appears as a hypodense masswith associated upstream ductal dilatation andparenchymal atrophy. The presence of an unobstructedmain pancreatic duct coursing through the hypodensemass-like process favors inflammatory pancreatic massover PDAC [32]. While, a well-demarcated mass withhomogenous enhancement compared to the backgroundparenchyma on post-contrast images favors carcinomaover pancreatitis [33]. Diffusion-weighted imaging inconjunction with other imaging features may help indistinguishing CP from PDAC as the apparent diffusion

Fig. 9. A 60-year-old woman with abdominal pain. A AxialCECT and B coronal CECT shows a large heterogeneouslyenhancing pancreatic head mass (arrows). Surgical resectionconfirmed Solitary fibrous tumor.

Fig. 10. A 50-year-old woman with abnormal liver functiontests. A Axial HASTE MRI image shows an ill-defined unci-nate mass (curved arrows). B Axial CEMRI image showsheterogeneous enhancement of the mass. Surgical resectionconfirmed marked chronic pancreatitis.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

Fig. 11. A 52-year-old woman with abdominal pain andjaundice. A Axial T2 MR image shows pancreatic ductaldilatation in the body and tail (solid white arrow). B Axial T2MR through the liver shows moderate intrahepatic biliarydilatation (dashed white arrows). C Axial CE T1 I image fromthe arterial phase of contrast enhancement shows ahypoenhancing pancreatic head lesion (curved arrow). D Ax-

ial CE T1 image at the same level but during the delayedphase of contrast enhancement shows hyperenhancement ofthe lesion compared to the background pancreas (arrow-head). E EUS shows a hypoechoic mass (black arrowheads).EUS-guided FNA was inconclusive. Serum IgG4 levels werenormal. Surgical resection was performed which confirmedautoimmune pancreatitis.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

coefficient (ADC) values in PDAC are lower than thegland, while in CP, these values are not significantlydifferent from the gland [34]. Tissue confirmation may beneeded to differentiate (Fig. 10).

Autoimmune pancreatitis

Autoimmune pancreatitis (aka lymphoplasmacytic pan-creatitis) is a form of chronic pancreatitis which canpresent with diffuse of focal enlargement of the pancreas.There are two distinct subtypes of autoimmune pancre-atitis on the basis of pathologic findings: type 1 (lym-phoplasmacytic sclerosing pancreatitis) and type 2(idiopathic duct-centric chronic pancreatitis). Type 1autoimmune pancreatitis is the pancreatic manifestationof IgG4-related disease, whereas type 2 has a distinctlydifferent histologic and clinical profile, with no elevationof serum IgG4 concentrations or the presence ofautoantibodies [35]. International Consensus DiagnosticCriteria for autoimmune pancreatitis include five cardi-nal features of type 1 autoimmune pancreatitis: pancre-atic imaging findings (parenchyma and duct), serologicfindings (elevated IgG4), histopathologic findings andimmunostaining, other organ involvement, and responseto steroid therapy [36].

Imaging appearance of the focal form includes focalenlargement of the pancreas which is isodense to hypo-dense to rest of the pancreas on the early phase withdelayed enhancement due to fibrotic component [37]. OnMRI, the affected area is usually mildly T2 hyperintense,T1 hypointense with hypoenhancement on the early post-contrast phase, and delayed hyperenhancement [38]. OnERCP, the stenosed main pancreatic duct segment islonger (> 30 mm) and the upstream ductal dilatation isusually less (< 6 mm) as compared to ductal obstructionwith PDAC [39]. There may be associated peripancreaticstranding (halo sign). Extrapancreatic organ involvementis relatively common. Most frequently involved systemsare biliary (cholangitis), kidneys (renal pseudotumors),salivary glands (sialadenitis), retroperitoneal fibrosis,and periaortitis [38]. The presence of extrapancreaticorgan involvement, elevated IgG4 levels, relative lack ofductal dilatation should raise suspicion for AIP(Figs. 11, 12).

bFig. 12. A 33-year-old woman with abdominal pain. A AxialHASTE MR image shows an ill-defined hyperintense mass-like process in the pancreatic body (white arrowhead). Thepancreatic duct upstream to this lesion is prominent (curvedarrow). B Axial CE T1 MR performed during the early venousphase shows hypoenhancement of the lesion compared tothe pancreas (white arrows). C A more delayed axial CE T1image at the same level shows delayed hyperenhancement ofthe lesion (dashed white arrows). EUS images (not shown)suggested inflammatory changes of pancreatitis. The chan-ges resolved after steroid therapy, consistent with diagnosisof focal AIP.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

Groove pancreatitis

This is a form of chronic pancreatitis which primarilyinvolves the pancreatic ‘‘groove’’ between pancreatichead, CBD, and duodenum. It is most commonly seen in

middle-aged alcoholic men [40]. Imaging appearance canrange from inflammatory change in the pancreaticgroove to the presence of curvilinear sheet-like soft tissuein the groove. There may be associated thickening of theduodenal wall with small cysts in the duodenal wall orthe groove itself. Most pancreatic adenocarcinomas donot show internal cystic change and duodenal wallthickening. PDACs are more likely to infiltrate posteri-orly in the retroperitoneum and encase vasculature [41](Fig. 13).

Anatomic variants

Focal fat

Focal fat replacement of the pancreas is a benign processwhich can be secondary to diabetes, obesity, chronicpancreatitis, hereditary pancreatitis, obstruction of thepancreatic duct by calculus or tumor, steroid therapy,and cystic fibrosis [42]. Fatty replacement is usually moresevere in anterior aspect of head of pancreas [43]. Al-though, the exact cause of this distribution is not known,it is presumably due to differences in histological char-acteristics of the two embryological pancreatic buds. Theventral bud forms the posterior part of the head andupper two-thirds or all of the uncinate. The dorsal budforms the anterior part of the head and rest of the pan-creas. Microscopically, the embryological dorsal pan-creas has more loose lobules of pancreatic parenchymawith larger amount of intralobular adipose tissue com-pared with the embryological ventral pancreas [44].

On non-contrast CT, focal fatty replacement mayshow negative fat attenuation [45]. However, on con-trast-enhanced CT, it might appear as a hypoattenuatingmass similar to PDAC. Preservation of normal pancre-atic contour and lobular appearance can help to differ-entiate between focal fatty replacement and PDAC. Withfocal fatty replacement, there is no dilatation of the mainpancreatic duct or CBD. The adjacent vessels are notinvaded and there is no associated adenopathy [45].Chemical shift opposed phase imaging MR images canbe more definitive as it shows a reduction in signal

bFig. 13. A 64-year-old man with history of alcohol use andabdominal pain. A Coronal CECT image shows an area of ill-defined low attenuation in the pancreatic head and the pan-creaticoduodenal groove (straight arrows). A small cyst isnoted in the pancreaticoduodenal groove (curved arrow).B Coronal CECT image at a different level shows prominenceof the main pancreatic duct (dashed white arrows). EUS-guided FNA was performed which showed acute and chronicinflammation suggesting groove pancreatitis. The patient wasmanaged conservatively. C Coronal CECT from the samepatient 3 years later, shows resolution of the low attenuationregion in the pancreatic head with persistent cystic changes inthe pancreaticoduodenal groove (white arrowhead).

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

intensity in the focal ‘‘mass’’ as opposed to PDAC whichdoes not contain lipid [42, 45] (Fig. 14).

Annular pancreas

This is a rare congenital variant in which the pancreaticparenchymal tissue encircles the duodenum. It can becomplete or incomplete and usual presenting symptomsare of gastric outlet obstruction or pancreatitis. Annularpancreas results from failure of the ventral bud to rotatewith the duodenum, resulting in envelopment of theduodenum [46]. There is frequent association with pan-

creatic divisum. The imaging appearance of a unopaci-fied second duodenum encircled by the pancreaticparenchyma can mimic a pancreatic head mass [47]. Ifthis is suspected based on CT imaging, secretin-enhancedMRI may be the best non-invasive way to differentiate todefine the pancreatic parenchymal and ductal anatomy[46] (Fig. 15).

Conclusion

Several neoplastic, inflammatory, and anatomic variantsmay mimic the imaging appearance of PDAC. Radiolo-

Fig. 14. A 60-year-old woman with abdominal pain. A AxialHASTE MRI images show mildly hyperintense mass in thepancreatic head (thick white arrow). B Axial CE T1 imagefrom the pancreatic phase shows hypoenhancement of thelesion compared to the pancreas (arrowhead). C Chemicalshift out of phase image shows signal drop out and India ink

artifact (thin white arrows). D Fat-only dixon image shows thepresence of fat within the lesion (curved arrow). EUS-guidedFNA was inconclusive. Surgical resection was performedwhich showed lack of malignancy and the presence of fattyinfiltration.

N. S. Gandhi et al.: Imaging mimics of pancreatic ductal adenocarcinoma

gists should be familiar with the presentation andimaging appearance of these entities to avoid unneces-sary invasive tests and surgeries.

Compliance with ethical standards

Funding This article was not part of any funded grant.

Conflict of interest None of the authors have any conflict of interestrelated to this article.

Ethical approval This article does not contain any studies with humanparticipants or animals performed by any of the authors.

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