Mistakes in ... Booklet 2020 - 26

ueg education

Mistakes in... 2020

investigations when clinical features or outcome
suggest malignancy.10

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b

c

Mistake 5 Failing to identify autoimmune
pancreatitis
Two subtypes of autoimmune pancreatitis (AIP)
have been described: type 1 is an IgG4-related
lymphoplasmacytic sclerosing pancreatitis,
whereas type 2 is an idiopathic, duct-centric
pancreatitis.9 Clinical presentation (jaundice,
abdominal pain, weight loss) and imaging features
(focal parenchymal enlargement) can falsely
suggest the presence of a malignant lesion and
erroneously lead to surgery.11 Typical features of
AIP include diffuse enlargement of the gland
with loss of globular contours, described as a
'sausage-like' appearance, minimal or absent
peripancreatic infiltration, a capsule-like rim
enhancement surrounding the pancreas,
and the absence of calcifications or vascular
encasement.11
Dynamic contrast-enhanced CT or MR
imaging may help differentiate focal AIP from
pancreatic adenocarcinoma. Both lesions
appear hypovascular in the pancreatic arterial
phase compared with the surrounding
parenchyma, but during the portal venous
phase, focal AIP may show some enhancement
while pancreatic adenocarcinoma usually
remains hypodense.11 MR imaging can further
assess pancreatic and biliary ducts, which may
present with narrowing, irregularity and
multifocal strictures with mild upstream
dilatation in patients with AIP.11
MRI diffusion-weighted imaging (DWI) is
a functional technique that reflects the
characteristics of tumour tissues, such as cellular
density and the integrity of cell membranes, based
on the erratic motion of water molecules that is
quantitatively expressed as an apparent diffusion
coefficient (ADC).1 Pancreatic adenocarcinoma
provokes a dense fibrotic process, which can give
a lower ADC value due to the restriction diffusion
often associated with fibrosis.1 Similarly, AIP will
also present with a low ADC, due to the increased
density of the pancreatic parenchyma associated
with periductal inflammation.12 A distinctive
feature that can differentiate the two diseases is the
impressive response to steroid treatment that is

a

b

Figure 7 | Pancreatic duct stricture. An MRCP image reveals a focal pancreatic duct stricture (arrow) (a) without
any measurable mass in axial T2W image (b) but with focal restriction in DWI (arrow) (c). EUS-guided fine needle
aspiration confirmed a pancreatic ductal adenocarcinoma of less than 2 cm. Reproduced with permission from
Zamboni GA, et al. Abdom Radiol (NY) 2020; 45: 1410-1419 © (2020) Springer Nature Switzerland AG.

experienced by 90% of patients with AIP, regarding
both clinical and imaging features (figure 5).9

Mistake 6 Thinking all hypervascular
pancreatic lesions are neuroendocrine
neoplasms
Pancreatic neuroendocrine neoplasms (PNENs)
are rare tumours that constitute approximately
1-3% of all pancreatic neoplasms.13 They
are often well-circumscribed solid lesions that
appear hyperattenuated on arterial and portal
venous phase CT images because of their rich
vascularity.13 These same features may also be
encountered in cases of intrapancreatic accessory
spleen (IPAS).11,14 Accessory spleen is a benign
condition in which splenic tissue is found outside
of the spleen, elsewhere in the abdomen and
pelvis, and it is found in approximately 10% of
adult patients in autopsy studies.14
The second most common location for IPAS
is the tail of the pancreas (16.7%), following the
perihilar area of the spleen.14 There are three CT
and MR signs in dynamic studies that may help
in differentiate IPAS from PNENs: location in the
dorsal surface of the pancreas, heterogeneous
enhancement in the arterial phase, and a similar
enhancement pattern to the spleen in venous and
late phases.15 Similarly, DWI or T2-weighted MRI
can likewise suggest IPAS if the lesion is isointense
with the spleen (figure 6).14
Further studies that can help refine the
diagnosis and avoid unnecessary surgery are
Technetium-99m sulfur colloid radiolabelled
heat-damaged red blood cells and endoscopic
ultrasound (EUS) guided fine needle aspiration
(FNA).11,14 On EUS IPAS appears hypoechoic or

c

Figure 6 | Intrapancreatic accessory spleen. An intrapancreatic accessory spleen (arrow) is seen as a focal
nodular lesion showing the same enhancing pattern of adjacent splenic parenchyma in arterial (a) and venous
(b) phase as well as the same signal intensity in DWI (c).

14

isoechoic, round or oval shaped, homogenous
with a smooth, well-demarcated border.
The echogenicity is similar to the splenic
echogenicity and the size is usually <2 cm.14 FNA
typically reveals a heterogeneous population of
lymphocytes with traversing small vessels over a
background of blood and mixed inflammatory cells
with CD8 positive immunostaining.14

Mistake 7 Relying on contrast enhanced
dynamics alone to detect pancreatic cancer
Pancreatic cancer can be overlooked on imaging
studies for various reasons such as lesion size or
perfusion dynamics.11 While the sensitivity for
detection of pancreatic adenocarcinoma >2 cm
is about 67-100%, it drops to 50-78% for the
detection of smaller tumours. This can be
worrisome because up to 30% of pancreatic
cancers are <2 cm at presentation.16
Furthermore, although the majority of pancreatic
adenocarcinomas appear hypoenhanced, in 11%
of cases they may appear isoenhanced to the
surrounding parenchyma.17
In the aforementioned situations,
detection may rely on secondary findings such
as pancreatic duct dilatation, glandular atrophy,
and abrupt ductal cut-off. Complete cut-off of a
portion of the pancreatic duct, as identified on
MRCP, in patients who have no other signs of
chronic pancreatitis, should always suggest the
possibility of malignancy. As mentioned before,
DWI can help in increasing diagnostic accuracy.1
Finally, EUS-FNA directed to the transition zone
may help to establish the final diagnosis, with a
sensitivity, specificity, positive predictive value,
and accuracy of 87.3%, 98.3%, 98.5%, and 92.1%,
respectively (figure 7).18

Mistake 8 Incorrectly identifying
pancreatic ductal anatomy (ex pancreas
divisum)
The dorsal duct drains the superior and anterior
portion of the pancreatic head, usually as a
separate duct terminating at the minor papilla,
which is located 10-15 mm above and to the right
of the major papilla. In approximately 60-70 %
of the population, the dorsal and ventral
pancreatic ducts have fused, resulting in a
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