Diagnostic Ultrasound - Abdomen and Pelvis

Solid Pancreatic Lesion
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Differential Diagnoses: Pancreas
DIFFERENTIAL DIAGNOSIS
Common
• Pancreatic Ductal Carcinoma
• Focal Acute Pancreatitis
• Chronic Pancreatitis
• Pancreatic Neuroendocrine Tumor
• Serous Cystadenoma of Pancreas
• Mucinous Cystic Neoplasm of Pancreas
Less Common
• Metastasis
• Lymphoma
• Solid Pseudopapillary Neoplasm
• Intrapancreatic Splenule
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Correlate with clinical information (e.g., history of
pancreatitis, obstructive symptomatology)
• Pancreatic duct dilatation favors diagnosis of pancreatic
ductal carcinoma
○ Biliary dilatation present as well in pancreatic head ductal
carcinoma
• Other ancillary findings to look for include
○ Cystic component
○ Internal septation
○ Presence of intralesional calcification
○ Vascular encasement
○ Regional lymph node and liver metastases
• Clues to detection of small tumor
○ Focal contour irregularity
○ Subtle pancreatic duct/bile duct dilatation
• CECT or CEMR improves ability to detect and characterize
solid pancreatic lesions
○ Can evaluate for vascular encasement
• Endoscopic ultrasound is invasive; however, increases
sensitivity for lesion detection and can be used to guide
biopsy for diagnosis
Helpful Clues for Common Diagnoses
• Pancreatic Ductal Carcinoma
○ Arises from ductal epithelium of exocrine pancreas
○ Location: Head of pancreas (60-70%), body (20%),
diffuse (15%), tail (5%)
○ Average size ~ 2-3 cm
○ Pathology: Scirrhous infiltrative adenocarcinoma with
dense cellularity and sparse vascularity
○ Typical US findings
– Poorly defined, homogeneous or heterogeneous,
hypoechoic mass
– Pancreatic duct dilatation upstream from tumor with
abrupt tapering at site of obstruction
– Bile duct dilatation seen in pancreatic head tumor
– Necrosis/cystic component is rarely seen
– Displacement/encasement of adjacent vascular
structures (e.g., superior mesenteric vessels, splenic
artery, hepatic artery, gastroduodenal artery)
– Presence of liver and regional nodal metastases
– Ascites due to peritoneal metastases
• Focal Acute Pancreatitis
○ Clinical information very important for correct imaging
interpretation
– Acute onset of epigastric pain, fever, and vomiting
– Raised serum amylase and lipase
– Presence of underlying predisposing factors: Biliary
stone, alcoholism, drugs (e.g., steroid), trauma, etc.
○ Focal, ill-defined, hypoechoic enlargement of pancreatic
parenchyma
– Heterogeneous appearance in cases with
intrapancreatic necrosis/hemorrhage
○ Blurred pancreatic outline/margin
○ Presence of peripancreatic fluid collection
○ Lack of pancreatic duct dilatation
○ No parenchymal calcification
• Chronic Pancreatitis
○ Longstanding clinical symptoms, recurrent attacks of
epigastric pain, typically radiates to back
○ Most common US features
– Diffuse atrophy
– Main pancreatic duct beading and side branch
dilatation
– Parenchymal and ductal calcifications
○ Can have focal involvement with mass-like appearance
○ Look for smoothly stenotic or normal main duct
penetrating abnormal region on MRCP
• Pancreatic Neuroendocrine Tumor
○ Functioning and nonfunctioning subtypes have distinct
appearances
– Functioning tumor usually small, solid, wellcircumscribed,
hypo-/isoechoic mass
– Nonfunctioning tumors tend to be larger with more
heterogeneous echo pattern due to necrosis,
calcification, and cystic change
– Solid components are typically hypervascular on
power Doppler US and hyperenhancing on CT and MR
○ Detection may be difficult with small functioning tumors
○ Endoscopic US detects tumors in pancreatic head and
body
○ Intraoperative US is useful for tumor localization
○ Liver and regional lymph node metastases seen in 60-
90% at clinical presentation
– Hyperechoic liver metastases more suggestive of
neuroendocrine tumors than ductal carcinoma
• Serous Cystadenoma of Pancreas
○ Commonly in pancreatic body and tail; 30% occur in
pancreatic head
○ Composed of tiny cysts separated by internal septations
○ Septa coalesce to form central echogenic scar with
"sunburst"calcification
○ US appearance depends on size of individual cysts
– Slightly echogenic, solid-appearing mass (small cysts
provide numerous acoustic interfaces)
– Partly solid-appearing mass with anechoic cystic areas;
cysts usually at periphery due to central scar
– Multicystic mass with internal septations and solid
component
○ Typically no pancreatic duct dilatation
– However, large lesions in head of pancreas can behave
more aggressively
○ Intralesional color Doppler flow in fibrovascular septa