Diagnostic Ultrasound - Abdomen and Pelvis

Mucinous Cystic Pancreatic Tumor
TERMINOLOGY
Abbreviations
• Mucinous cystic pancreatic tumor (MCN)
Synonyms
• Mucinous cystic neoplasm of pancreas
• Mucinous cystadenoma/cystadenocarcinoma
• Macrocystic cystadenoma/cystadenocarcinoma
• Macrocystic adenoma
Definitions
• Septated cystic neoplasm composed of mucin-producing
epithelium and distinctive ovarian-type stroma, ranging in
grade from potentially malignant to invasive carcinoma
IMAGING
General Features
• Best diagnostic clue
○ Thick-walled, multilocular cystic mass with internal
septations and possibly mural nodularity
• Location
○ Body and tail of pancreas (more common)
• Size
○ Range from 2 cm to > 10 cm in diameter
○ Mean size 8.7 cm
Ultrasonographic Findings
• Grayscale ultrasound
○ Well-circumscribed, anechoic, or hypoechoic mass,
commonly in pancreatic body or tail
○ Unilocular or multilocular with echogenic septations
– Cyst contents may be anechoic, echogenic with debris,
± solid component
○ No communication with pancreatic ductal system
○ May contain calcification
○ Mural nodularity suggests malignancy
– When malignant: Possible adenopathy ± thick-walled
cystic liver lesions
• Color Doppler
○ Hypovascular mass
○ May encase splenic vein or displace surrounding vessels
• Findings on US are nonspecific and further evaluation with
CT or MR is necessary
CT Findings
• CECT
○ Well circumscribed and smoothly marginated
○ Unilocular or multilocular low-attenuation cystic lesion
– When multiloculated, typically contains fewer than 6
cystic components
– Each > 2 cm in size
○ May show peripheral curvilinear or septal calcification
○ Enhancement of cyst wall, internal septations and any
mural nodules
○ Features favoring malignancy
– Solid mural nodules
– Thick septations
– Wall thickening
MR Findings
• T1WI
○ Variable signal intensity based on cyst content
– May be hypointense, isointense, or hyperintense on FS
T1, depending on proteinaceous content
○ Hypointense focal calcifications
• T2WI
○ T2 hyperintense cysts with mixed signal of internal septa
○ T2 hypointense capsule and calcifications
• T1WI C+
○ Enhancement of fibrous cyst wall on more delayed postcontrast
sequences
○ Features suggesting malignancy
– Enhancing septations and solid components
• MRCP
○ Pancreatic duct may be displaced or narrowed by mass
○ Confirms absence of communication with pancreatic
duct
Other Modality Findings
• Endoscopic ultrasound (EUS)
○ High spatial resolution; can depict internal septations,
mural nodules, wall thickness
○ Can guide aspiration of fluid and biopsy of solid
components, increasing overall accuracy for diagnosis
over CT and MR
– Cyst contents
□ High CEA (< 5 ng/mL virtually excludes mucinous
lesion)
□ Low amylase (though can be increased)
□ When malignant high CA 19.9 level
□ Positive mucin stain
Imaging Recommendations
• Best imaging tool
○ CT or MR
– Provides accurate characterization of cyst morphology
○ EUS
– Invasive technique
– Often performed in conjunction with cyst fluid
aspiration for definitive diagnosis
• Protocol advice
○ CT or MR should be performed with contrast
enhancement
– Dual-phase pancreatic protocol (late arterial and
portal venous phases)
– Improves sensitivity for depicting morphological
features, including internal septation and mural
nodularity
○ MRCP
– To characterize relationship between lesion and
pancreatic duct
DIFFERENTIAL DIAGNOSIS
Pseudocyst
• Unilocular anechoic or hypoechoic cyst with no septations
or solid components
• May show communication to pancreatic duct
• Peripancreatic fat plane infiltration
• Clinical history of pancreatitis
Diagnoses: Pancreas
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