cystic pancreatic lesions

2. Purpose is to illustrate
The spectrum of imaging findings of cystic pancreatic
lesions and highlight the roles, advantages, and
limitations of various imaging modalities in the
differential diagnosis of pancreatic cystic lesions, with
particular emphasis on pseudocysts versus
nonpseudocysts

3. LEARNING OBJECTIVES
Identify the radiologic findings of pancreatic
pseudocysts.
Describe the radiologic findings of cystic pancreatic
neoplasms.
Discuss the findings that allow differential diagnosis
between pancreatic pseudocysts and cystic pancreatic
neoplasms.

4. Pancreatic Pseudocyst
Pseudocysts are the most common cystic lesions
of the pancreas.
wide application of computed tomography (CT)
and ultrasound (US) in asymptomatic and mildly
symptomatic patients has increased detection of
incidental cystic lesions of the pancreas so that
the differential diagnosis of pancreatic cystic
lesions has become more challenging.
Differentiating pancreatic pseudocysts from
nonpseudocysts is important for determining
treatment.

5. Radiologic imaging alone has limited accuracy in
differentiating between pseudocysts and
nonpseudocysts due to similarities in the imaging
findings of the lesions
Thin-section CT and magnetic resonance (MR)
cholangiopancreatography have gained popularity
for the potential advantages of visualizing
communication between the main pancreatic
duct and a cystic lesion noninvasively.

6. Endoscopic US has emerged as a modality that
can provide anatomic structure in greater detail
and facilitate aspiration biopsy of smaller lesions.
When radiologic imaging findings and results of
cyst fluid analysis with or without biopsy are
interpreted in conjunction with a careful patient
history, diagnostic accuracy may be increased
substantially.

7. Most cystic masses of the pancreas encountered in clinical
practice are postinflammatory pseudocysts
Pancreatic pseudocysts are defined as “localized amylase-
rich fluid collections located within the pancreatic tissue
or adjacent to the pancreas and surrounded by a fibrous
wall that does not possess an epithelial lining.”
The CT findings of a pseudocyst include a round or oval
fluid collection with a thin, barely perceptible wall or thick
wall that shows evidence of contrast enhancement.

8. They develop most often as a complication of
acute or chronic pancreatitis and may develop
secondary to pancreatic trauma or surgery
Clinical scenarios
pseudocyst developing after identifiable acute
pancreatitis
a pseudocyst resulting from an acute incident
superimposed on chronic pancreatitis
pseudocyst with an uncertain or no known
previous clinical history of pancreatitis.

9. Classic Postinflammatory Pancreatic
Pseudocyst
After an acute attack, the pseudocyst develops during a
period of 4–6 weeks. Pseudocysts may be followed
conservatively if they are smaller than 6 cm in diameter or
the patient is asymptomatic because pseudocysts can
resolve spontaneously
Unilocular pseudocysts occur more frequently than
multilocular pseudocysts.
Complications related to pseudocysts include infection,
hemorrhage, rupture, and obstruction of other abdominal
organs. Secondary infection of the pseudocyst is a dreaded
complication due to its high rate of morbidity and
mortality, requiring drainage by radiologic, endoscopic, or
surgical decompression

10. Figure 1a. Developing pseudocyst in a 63-year-old woman with epigastric pain. (a)
Unenhanced CT scan shows an edematous pancreas and an ill-defined, acute fluid collection
surrounding the tail of the pancreas (arrow) with peripancreatic inflammatory changes, an
appearance compatible with acute pancreatitis

11. Figure 1b. Developing pseudocyst in a 63-year-old woman with epigastric pain. On a follow-up
contrast-enhanced CT scan obtained 1 month later, the lesion appears as a bilobed cystic mass
with a septum in the pancreatic body and tail (arrow). The peripancreatic inflammatory changes
are markedly decreased.

12. Figure 1c. Developing pseudocyst in a 63-year-old woman with epigastric pain. On
a follow-up CT scan obtained 2 years later, the lesion appears as a unilocular, low-
attenuation fluid collection with a well-defined thin wall (arrow). This is the typical
appearance of a postinflammatory pseudocyst.

13. Figure 2a. Progressive evolution and spontaneous resolution of a
pancreatic pseudocyst in a 31-year-old man with left upper quadrant pain.
(a) Initial contrast-enhanced CT scan shows an edematous pancreas and
peripancreatic inflammatory changes, an appearance compatible with
acute pancreatitis

14. Figure 2b. Progressive evolution and spontaneous resolution of a pancreatic pseudocyst in
a 31-year-old man with left upper quadrant pain. Follow-up CT scan obtained 2 months later
shows a relatively thick-walled cyst in the pancreatic tail (arrow). This lesion represents a
maturing pseudocyst.

15. Figure 2c. Progressive evolution and spontaneous
resolution of a pancreatic pseudocyst in a 31-year-old man
with left upper quadrant pain. CT scan obtained 4 months later
shows resolution of the pseudocyst.

16. Pancreatic Pseudocyst Superimposed on
Chronic Pancreatitis
Pancreatic pseudocysts can occur in association with
chronic pancreatitis as chronic pseudocysts or can result
from acute exacerbation of pancreatitis or chronic
pancreatitis.
 In the former case, a distinct clinical history of acute
pancreatitis may be lacking and the pseudocyst is often
detected incidentally, in comparison with the latter case.
The recognition of a pancreatic pseudocyst resulting from
chronic pancreatitis is usually easy when there are
associated stigmata of chronic pancreatitis such as
parenchymal calcifications or ductal stones, ductal
dilatation, and atrophy of the parenchyma (Fig 5).

17. Figure 5a. Chronic pancreatitis with an intrapancreatic pseudocyst in a
42-year-old man with a history of alcoholic pancreatitis. (a) Contrast-
enhanced CT scan shows a dilated pancreatic duct (arrows) with mild
pancreatic atrophy, an appearance compatible with chronic pancreatitis

18. Figure 5b. Chronic pancreatitis with an intrapancreatic pseudocyst in a
42-year-old man with a history of alcoholic pancreatitis. a round mass with
diffuse low attenuation in the pancreatic head (curved arrow). The mass
represents a pseudocyst. Note the dilated pancreatic duct (straight arrow).

19. Figure 5c. Chronic pancreatitis with an intrapancreatic pseudocyst in a
42-year-old man with a history of alcoholic pancreatitis.. (c) Contrast-
enhanced CT scan shows pancreatic calcifications (arrow), a finding
compatible with chronic pancreatitis.

20. Pancreatic Pseudo-cyst without an
Antecedent Episode of Acute Pancreatitis
Incidental pancreatic cysts are smaller than symptomatic
cysts and are unlikely to be pseudocysts.
Cystic pancreatic neoplasm should be considered in the
differential diagnosis of a pancreatic cyst, even in patients
with a history of pancreatitis, if no recent episode of acute
pancreatitis can be documented on clinical or imaging
grounds.
 For pancreatic pseudocysts without an antecedent
episode of acute pancreatitis and radiologic evidence of
pancreatitis, US-, CT-, or endoscopic US–guided aspiration
or biopsy or at least a follow-up study should be
recommended.

21. Figure 4. Hemorrhagic pseudocyst in a 45-year-old man who experienced an episode of
abdominal pain but had no clinical findings suggestive of infection. Contrast-enhanced CT
scan shows a cystic mass containing an area of high attenuation (arrow), a finding consistent
with recent hemorrhage.

22. Figure 6a. Incidentally detected pancreatic pseudocyst in a 77-year-old
woman with no known history of pancreatitis. (a) Image obtained with thin-
section (2.5-mm section thickness) contrast-enhanced multidetector CT
shows an ovoid hypoattenuating mass without internal septa or mural
nodules in the pancreatic tail (arrow).

23. Cystic Neoplasms
uncommon
increasingly being detected and are difficult to distinguish from
pseudocysts, which are encountered far more frequently.
D/d
serous cystadenoma
mucinous cystic neoplasm
IPMT
solid and papillary epithelial neoplasm (SPEN) and
cystic islet cell tumor
the average size of detected lesions has steadily decreased and
imaging characterization becomes more difficult for smaller
lesions.

24. Serous Cystadenoma
also referred to as microcystic cystadenoma
typically found in women over the age of 60 years
with nonspecific complaints of abdominal pain or
weight loss or more commonly as an incidental
finding.
multiple cysts varying in size from 0.2 to 2.0 cm,
and the size of the tumors ranges in greatest
dimension from 1.4 to 27 cm
A central stellate scar with calcification, which is
known to be characteristic of serous cystadenoma,
may sometimes be observed

25. Continue…
Internally, the cyst has a honeycombed appearance
compatible with innumerable cysts. At US, the lesion may
appear as a solid echogenic mass due to interfaces
produced by the numerous cysts. It may appear as a solid
mass at CT, depending on the size of the cysts and the
amount of fibrous tissue
Asymptomatic serous cystadenomas do not require
surgical excision because they are rarely malignant.
Tumors smaller than 2 cm have been reported and are
more likely to be serous cystadenomas
Macrocystic or oligocystic serous cystadenoma is a variant
of serous cystadenoma that is very difficult to differentiate
from mucinous cystadenoma

26. Figure 7a. Serous cystadenoma in a 45-year-old woman with right upper
quadrant pain. (a) Contrast-enhanced CT scan shows a low-attenuation
mass with a honeycomb appearance in the pancreatic head and uncinate
process (arrow). The honeycomb appearance is produced by numerous
tiny cystic structures

27. Figure 7b. Serous cystadenoma in a 45-year-old woman with right upper
quadrant pain. (b) US scan shows that the mass has low echogenicity due
to the interfaces between the tiny cysts. Note the increased through
transmission posterior to the mass

28. Figure 7c. Serous cystadenoma in a 45-year-old woman with right upper
quadrant pain. Photograph of the cut surface of the specimen shows
innumerable cysts.

29. Location in the pancreatic head, lobulated contour,
and lack of wall enhancement have been reported to
be specific for macrocystic serous cystadenoma in
comparison with mucinous cystic tumor.
Lobulated contours have been reported to be a
specific finding in comparison with pseudocyst.

30. Oligocystic serous cystadenoma in a 56-year-old woman with epigastric pain. (a,
b) US scan (a) and CT scan (b) show a well-demarcated cystic mass with
peripheral internal septa (arrow) in the pancreatic head. Note the peripheral septum
with calcification (arrow in b)

31. Figure 9b. Oligocystic serous cystadenoma in a 56-year-old woman with
epigastric pain. (a, b) US scan (a) and CT scan (b) show a well-demarcated
cystic mass with peripheral internal septa (arrow) in the pancreatic head. Note the
peripheral septum with calcification (arrow in b)

32. Figure 9c. Oligocystic serous cystadenoma in a 56-year-old woman with
epigastric pain. (c) Endoscopic pancreatogram shows the pancreatic duct splayed
by the tumor. No communication exists between the lesion and the main duct

33. Mucinous Cystic Neoplasms
most common cystic tumors of the pancreas
large cystic spaces are lined by tall, mucin-
producing columnar cells.
Mucinous cystic neoplasms may be unilocular or
mutilocular and are commonly detected only after
achieving a large size.
Solid papillary excrescences sometimes protrude
from the wall into the interior of these tumors.
The absence of excrescences does not exclude
malignancy.

34. Figure 10. Incidentally detected mucinous cystadenoma in a 67-year-old
woman. Contrast-enhanced CT scan shows a complex cystic mass with a
few septa in the pancreatic tail (arrow).

35. Figure 11. Mucinous cystadenoma in a 47-year-old woman with left
upper quadrant pain. Contrast-enhanced CT scan shows a large cystic
tumor with small cysts clustered at its periphery (arrow).
.

36. Multiple enhancing septations and solid intramural
nodules are typical radiologic findings of mucinous cystic
neoplasms
Peripheral calcification, which can be seen in 10%–25%, is
an important characteristic for mucinous cystic neoplasms
and can be used to differentiate them from serous
cystadenomas, which are known to have central
calcification.
Endoscopic US can depict the internal architecture of the
cystic mass, including internal septa and tiny solid
components, better than conventional CT, depending on
the location of the tumor and patient body habitus.

37. tumors are round to oval with a smooth external
surface. Secondary cysts along the internal wall
are common. Occasionally, communication
between the pancreatic duct and the cystic
neoplasm is present.
Mucinous cystic tumors should always be
resected because they are all potentially
malignant. When the cyst is small in an
asymptomatic patient, cyst aspiration and analysis
of the cyst fluid can be helpful in differential
diagnosis

38. Mucinous Cystic Neoplasm Misdiagnosed as
a Pseudocyst
Owing to partial volume averaging with the
hypoattenuating cyst fluid, the fine internal septa
and small intramural nodules may not be visible
at conventional contrast-enhanced CT. This
explains why mucinous cystic neoplasm
sometimes is misdiagnosed as a pseudocyst
So to avoid this better is to use multidetector CT

39. Figure 12. Mucinous cystadenocarcinoma in a 52-year-old woman with epigastric
pain. Despite the absence of a history of pancreatitis, the thin cyst wall led to the
presumptive diagnosis of a pseudocyst. CT scan shows a thin-walled cyst in the
pancreatic tail. There is a tiny peripheral intramural nodular structure (arrow), which
was initially overlooked. At surgery, the lesion proved to be a mucinous
cystadenocarcinoma.

40. Figure 13a. Incidentally detected mucinous cystadenoma in a 65-year-old
woman. (a) Contrast-enhanced CT scan shows an ovoid hypoattenuating mass
with barely visible septa in the pancreatic head (arrow). (b) Endoscopic US scan
shows the complex cystic mass with multiple internal septa (arrow). Endoscopic
US–guided fine-needle aspiration was performed, and cytologic analysis revealed
abundant mucin with scant glandular epithelial cells, findings suggestive of a mucin-
producing tumor. At surgery, the lesion proved to be a mucinous cystadenoma.

41. Figure 13b. Incidentally detected mucinous cystadenoma in a 65-year-old woman. (a)
Contrast-enhanced CT scan shows an ovoid hypoattenuating mass with barely visible septa in
the pancreatic head (arrow). (b) Endoscopic US scan shows the complex cystic mass with
multiple internal septa (arrow). Endoscopic US–guided fine-needle aspiration was performed,
and cytologic analysis revealed abundant mucin with scant glandular epithelial cells, findings
suggestive of a mucin-producing tumor. At surgery, the lesion proved to be a mucinous
cystadenoma.

42. Intraductal Papillary Mucinous Tumor
IPMT is characterized by the papillary proliferation of
pancreatic ductal epithelium and production of mucin.
It is characterized by cystic dilatation of a main or a side
branch duct that contains thick mucoid secretions.
Patients present with nonspecific abdominal symptoms
and sometimes hyperamylasemia.
typically occur in elderly patients and are more common
in men.
 Although the incidence of IPMT seems to be increasing,
the likely explanation is increased use of imaging and
awareness of this disease entity.

43. IPMTs are classified into:-
main duct type
branch duct type
and combined type.
Accordingly, imaging findings vary depending on the
type of the tumor..

44. The side branch duct type is the most commonly
mistaken for mucinous cystic tumor or
pseudocyst.
Typical location (uncinate process), typical
appearance (grapelike locular appearance), and
communication with the duct at endoscopic
retrograde cholangiopancreatography (ERCP)
usually separate it from other lesions in the
pancreas.
A markedly dilated uncinate branch filled with
mucus is a typical feature of a side branch IPMT

45. ERCP is regarded as the modality of choice in the
diagnosis of IPMT for its ability to depict the bulging
ampulla of Vater, mucin pouring from the papilla, and
communication between the pancreatic duct and the cyst
cavity.
 Communication between the duct and the abnormal
cystic structure can be shown with thin-section helical CT
or with MR imaging and MR cholangiopancreatography.
 Although the classic diagnostic role of ERCP has been
challenged to some extent by combined use of MR
cholangiopancreatography and endoscopic US in the
evaluation of IPMT, ERCP has a distinctive diagnostic role
where the diagnosis is not clear on cross-sectional images.

46. Figure 14a. Multiple branch duct type of IPMT. (a) Contrast-enhanced CT scan
shows multiple cystic masses (straight arrow) in the pancreatic head and body.
Note the dilated pancreatic duct (curved arrow)

47. Figure 14b. Multiple branch duct type of IPMT. (a) Contrast-enhanced CT scan shows multiple cystic
masses (straight arrow) in the pancreatic head and body. Note the dilated pancreatic duct (curved arrow).
(b) Curved coronal reformatted view obtained along the pancreatic tail shows a communication between a
cystic mass and the dilated distal pancreatic duct (arrow).

48. Solid and Papillary Epithelial
Neoplasm
are histologically distinctive neoplasms of low
malignant potential with a favorable prognosis.
 SPEN is typically found in young women.
 Most patients present with nonspecific signs and
symptoms including nausea, vomiting, and abdominal
pain or fullness.

49. The tumor tends to be a large, well-circumscribed,
and slowly growing mass.
 The tumor may have a variety of internal
appearances, from purely cystic to completely solid,
but is usually surrounded by a thick, well-defined rim.
The appearance of the internal architecture typically
depends on the degree of hemorrhage and necrosis of
the tumor.

50. Figure 17a. SPEN in a 32-year-old woman with epigastric pain. (a) Contrast-enhanced CT
scan shows a mixed solid and cystic mass in the pancreatic head (arrows).

51. Figure 17b. SPEN in a 32-year-old woman with epigastric pain. (b)
Axial T1-weighted MR image (500/20) shows areas of high signal intensity
due to hemorrhage within the mass (arrow).

52. Multidetector CT and MR Imaging
with MR
Cholangiopancreatography
The improved multiplanar capability, thin
collimation, and ability to optimize parenchymal
enhancement of multidetector CT not only improve
the detection rate of the cystic pancreatic lesion but
may enhance diagnostic accuracy by depicting fine
internal architecture and the anatomic relationship
between the main pancreatic duct and the cystic
lesions

53. Image-guided Fine-Needle
Aspiration Biopsy
can be obtained by conventional US- or CT-guided
percutaneous needle aspiration or by an endoscopic
US–guided technique.
Analysis of the cystic contents includes viscosity,
enzymes (amylase, lipase), tumor markers
(carcinoembryonic antigen [CEA], cancer antigen 19-9
[CA 19-9]), and cytologic findings, which may help
differentiate between neoplastic cysts and
pseudocysts.

54. Endoscopic US and US-guided
Fine-Needle Aspiration or Biopsy
 provides more detailed anatomic information about
the cyst than conventional US
allows the sampling of both cyst fluid and any solid
component in smaller lesions.

55. Conclusions
Despite a remarkable increase in the number of cystic lesions of
the pancreas detected in clinical practice, the number of cystic
neoplasms misdiagnosed as pseudocysts has decreased.
The likely explanation is the increasing use of various imaging
modalities and image-guided aspiration and biopsy. If the
patient has no history of pancreatitis and no history of
pancreatic trauma or pancreatic surgery and the findings from
imaging do not allow conclusive diagnosis, a follow-up imaging
study or image-guided aspiration/biopsy should be
recommended.
