Diagnostic Ultrasound - Abdomen and Pelvis

Serous Cystadenoma of Pancreas
TERMINOLOGY
Abbreviations
• Serous cystadenoma (SCA)
Synonyms
• Pancreatic serous cystic neoplasm (SCN), glycogen-rich
cystadenoma, microcystic adenoma of pancreas
Definitions
• Benign epithelial neoplasm arising from centroacinar cells
of the exocrine pancreas, and composed of small cysts
containing proteinaceous fluid separated by fibrovascular
connective tissue septa.
IMAGING
General Features
• Best diagnostic clue
○ Solitary, honeycomb or sponge-like mass with central
radiating scar
• Location
○ Commonly in the body and tail; 30% in pancreatic head
• Size
○ Variable sizes; mean: 4.9 cm
○ Giant SCA ( >10 cm) are rare
• Morphology
○ Lobulated, well-demarcated, cystic mass
○ 2 morphologic types based on WHO subclassification:
– Serous microcystic adenomas: Honeycomb (20-40% of
cases) or polycystic
– Serous oligocystic adenoma/macrocystic variant (<
10% of cases): Usually unilocular or fewer larger cysts
(> 2cm)
Ultrasonographic Findings
• Grayscale ultrasound
○ Well-demarcated, lobulated, heterogeneous mass with
posterior acoustic enhancement
○ Generally → solid echogenic appearance due to
interfaces between cysts
– Slightly echogenic, solid-appearing mass (many
interfaces between numerous small cysts)
– Multicystic mass with septa and solid-appearing
component
□ Anechoic cystic areas usually in periphery
□ Central echogenic area = central scar (present in
30% of cases); ± calcification
– Macrocystic variant: Anechoic cyst ± a few septa
○ Pancreatic and common bile duct dilatation not typical
• Color Doppler
○ Increased vascularity within septa
CT Findings
• Microcystic form: Classic honeycomb pattern
○ Thin wall with enhancing septa delineating small cysts
– Cluster of > 6 cysts; each typically < 1 cm
– Coalescing septa may form characteristic central
stellate scar ± calcification
– May mimic solid mass if cystic locules are small and
enhancing septa predominate
○ Polycystic pattern: Multiple cysts ≤2 cm separated by
enhancing fibrous septa ± calcification
• Macrocystic serous cystadenoma: Usually unilocular
○ One/ few locules; thin nonenhancing imperceptible wall
MR Findings
• Can help identify cystic locules in tumors that appear solid
on US and CT
• T1WI: Hypointense tumor, central scar and calcification
○ Rarely may see intratumoral hemorrhage → varied signal
intensity
• T2WI: Hyperintense cystic components, hypointense septa,
central scar, and calcification
• T1WI C+: Delayed enhancement of septa and central scar
• MRCP: No communication to the pancreatic duct
Other Modality Findings
• Endoscopic ultrasound (EUS)
○ Higher spatial resolution than transabdominal
ultrasound → often diagnostic for microcystic form:
– Well-delineated honeycomb appearance with central
stellate scar (microcystic type)
– Poorly developed cyst wall
– Thin internal septa; hypervascular on Doppler
○ Can be used to guide fine needle aspiration (FNA) of cyst
fluid for indeterminate cases eg macrocystic variant
– Low viscosity, amylase, and CEA levels (< 5ng/mL)
Imaging Recommendations
• Best imaging tool
○ Contrast enhanced CT or MR
○ EUS: Improves characterization of lesion morphology
and can guide cyst aspiration/biopsy
– Invasive technique
– Presumptive diagnosis based on typical microcystic
features
– EUS-FNA when EUS appearance is nonspecific
• Protocol advice
○ In patients with thin body habitus, higher frequency
transabdominal US transducer help to depict small cysts
within the mass
○ Careful examination for subtle pancreatic calcification
DIFFERENTIAL DIAGNOSIS
Pancreatic Pseudocyst
• Most common cystic pancreatic lesion
• Collection of pancreatic fluid encapsulated by fibrous tissue
• Shows well-defined capsule vs. imperceptible wall of SCA
• Usually unilocular, no septa, solid component, or central
calcification
• Pancreatitis present or history of previous pancreatitis
Mucinous Cystadenoma of Pancreas
• Multiloculated cystic mass with echogenic internal septa
• May be indistinguishable from macrocystic SCA by imaging
• Most commonly located in tail of pancreas
• Thicker wall with calcification that tends to be peripheral
• Internal solid component suggests malignant tumor
Intraductal Papillary Mucinous Neoplasm (IPMN)
• Low grade malignancy arises from main pancreatic duct
(MPD) or side branch pancreatic duct (SBD)
Diagnoses: Pancreas
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