Endosonography in the diagnosis and management of pancreatic cysts

Table 1 Characteristics of common pancreatic cystic lesions

Characteristic	Pseudocyst	SCA	MCN	MD-IPMN1	BD-IPMN1	SPEN
Male:female	1:1	1:4	Nearly all female	2:1	2:1	1:4
Age (yr)	40-70	60-80	30-50	60-80	60-80	20-30
Location	Any	Any	Body, tail (90%)	Any (head and uncinate 50%)	Any (head and uncinate 50%)	Body, tail (60%)
Imaging features	Unilocular, thick or thin walled	Multilocular, lobulated. Typically microcystic appearance. Central scar	Unilocular, smooth and encapsulated. Septations and peripheral calcifications possible	Diffuse or focal main duct dilation. Fish-mouth papilla with visible mucus	Dilated side branches. Lobular with septations. “Bunch of grapes” appearance	Unilocular, encapsulated with solid and cystic structure. Hemorrhagic components
Communication with main duct	Variable	None	None	Yes	Yes	None
Cytology	Cyst contents	Cuboidal cells. Glycogen (+), PAS (+) and hemosiderin-laden macrophages	Columnar cells. Atypia varies. Mucin (+)	Columnar cells. Atypia varies. Mucin (+)	Columnar cells. Atypia varies. Mucin (+)	Branching papillae and fibrovascular stroma. Vimentin (+), chromogranin (-) and keratin (-)
Amylase (U/L)	> 250	< 250	< 250	> 250	> 250	N/A
CEA (ng/mL)	< 5	< 5	> 192	> 192	> 192	N/A
KRAS mutation	None	None	Yes	Yes	Yes	N/A
Malignant potential	None	Very rare	Yes (6%-27%)	Yes (40%-70%)	Yes (15%-20%)	Yes (2%-15%)
Morphological predictors of malignancy	None	None	> 6 cm, solid component, peripheral nodules or calcifications	Main duct ≥ 8 mm, solid component, nodules	≥ 3 cm, solid component, nodules, main duct ≥ 1 cm, and suspicious/malignant cytology	None

¹Mixed IPMN have features of both MD and BD-IPMN. SCA: Serous cystadenoma; MCN: Mucinous cystic neoplasm; MD-IPMN: Main duct intraductal papillary mucinous neoplasm; BD-IPMN: Branch duct intraductal papillary mucinous neoplasm; SPEN: Solid pseudopapillary neoplasm; PAS: Periodic acid-Schiff stain; CEA: Carcinoembryonic antigen.

Table 2 Endoscopic ultrasound features suggestive of mucinous or malignant cysts

EUS Feature	Type of cyst	Concerning for increased risk of malignancy
Size	-	> 3 cm
Shape	Smooth unilocular: pseudocyst or MCNLobular, multilocular: SCA or BD-IPMN	-
Number of cysts	Multiple: BD-IPMN	-
Calcifications	Central scar: pathognomonic for SCA Peripheral calcification: pseudocyst, SPEN, MCN	Peripheral calcification in MCN
Cyst wall	Thick: pseudocyst, cystic neuroendocrine, MCN, SPEN	Thick
Septa	-	Thick
Nodule	-	Presence
Solid mass	-	Presence
Debris	Pseudocyst	-
Pancreatic duct diameter	Dilated > 5 mm: MD-IPMN or mixed IPMN	Dilated > 8-10 mm
Communication with pancreatic duct	IPMN, pseudocyst	-

EUS: Endoscopic ultrasound; MCN: Mucinous cystic neoplasm; SCA: Serous cystadenoma; BD-IPMN: Branch duct intraductal papillary mucinous neoplasm; MD-IPMN: Main duct intraductal papillary mucinous neoplasm; SPEN: Solid pseudopapillary neoplasm; IPMN: Intraductal papillary mucinous neoplasm.

Table 3 Endoscopic ultrasound-fine needle aspiration cyst fluid analysis

Cyst fluid marker	Type of cyst	Sensitivity	Specificity
CEA < 5 ng/mL	SCA, pseudocyst, neuroendocrine tumor	54%	94%
CEA >192 ng/mL	Mucinous cyst (MCN or IPMN)	73%	84%
CEA > 800 ng/mL	Mucinous cyst (MCN or IPMN)	98%	48%
Amylase < 250 U/L	Excludes pseudocyst	44%	98%
KRAS mutation + LOH	Malignant cyst	37%	96%
KRAS mutation	Mucinous cyst (MCN or IPMN)	54%	100%

CEA: Carcinoembryonic antigen; SCA: Serous cystadenoma; MCN: Mucinous cystic neoplasm; IPMN: Intraductal papillary mucinous neoplasm; LOH: Loss of heterozygosity.