“Macrocystic” pattern: Few (< 6) macrocystic locules, which are relatively large (> 2 cm)
Usually of simple fluid attenuation, but may be mildly hyperdense due to hemorrhage or protein
Frequent peripheral curvilinear calcifications or calcifications in septations (16% of cases)
Presence of thick wall, mural nodularity, or thick septations suggests invasive malignancy
No apparent communication with main pancreatic duct
• MR: Usually simple fluid signal (high T2; low T1), but may be slightly less T2 hyperintense due to mucin content
Internal septations (which are T2 hypointense) easier to perceive on MRI compared to CT
MRCP: No communication with main pancreatic duct
PATHOLOGY
• Tumor shares clinical and pathologic characteristics of biliary tumors, ovarian tumors, and IPMN
• Presence of ovarian stroma lining cyst is key feature for diagnosis of mucinous cystic neoplasm (MCN)
CLINICAL ISSUES
• Strong preponderance in middle-aged women (99%)
• Considered premalignant or frankly malignant: Rate of malignancy in different series ranges between 10-40%
• Risk factors for invasive malignancy: Older age, lesion size, mural nodularity, thick wall, patient symptoms (pain, pancreatitis), and ↑ CEA and CA 19-9
• MCNs typically undergo complete surgical resection with adjuvant chemotherapy for malignant lesions
• Malignant MCNs receive adjuvant chemotherapy after surgical resection
(Left) Graphic of a mucinous cystic tumor shows a multiseptate, mucin-filled, cystic mass in the pancreatic tail that displaces the pancreatic duct.
(Right) Axial CECT in a 35-year-old woman demonstrates a large complex cystic mass arising from the pancreatic tail with multiple internal cystic locules and septations, some of which are thick . This mass was found to be a mucinous cystic neoplasm (MCN) with invasive adenocarcinoma at surgery.
(Left) Axial CECT in a 46-year-old woman demonstrates a large, simple-appearing cyst arising from the upstream pancreatic body.
(Right) Axial T2 FS MR in the same patient confirms the lack of complexity within the T2-hyperintense cyst . MR can sometimes show complexity and suspicious features that might be difficult to identify on CT. This was found to be a MCN with low-grade dysplasia at surgery.
TERMINOLOGY
Synonyms
• Mucinous cystic neoplasm (MCN), mucinous macrocystic neoplasm or adenoma, mucinous cystadenoma or cystadenocarcinoma
Definitions
• Thick-walled, unilocular or multilocular pancreatic tumor composed of large, mucin-containing cysts
Some sources suggest presence of ovarian stroma within lesion is necessary for diagnosis
• MCN and intraductal papillary mucinous neoplasm (IPMN) are together classified as pancreatic mucinous tumors
IMAGING
General Features
• Best diagnostic clue
Large, unilocular or multilocular encapsulated cystic mass with septations and thick wall in pancreatic tail
• Location
Tail of pancreas (more common)
Presents as single lesion (not multifocal like IPMN)
• Size
2-12 cm in diameter
– MCNs usually larger than serous cystadenoma or IPMN
Size is predictor of biologic behavior
– Lesions < 40 mm found to have low risk of malignancy in recent series
• Morphology
Typically round/ovoid, but may be ill defined/irregular
Radiographic Findings
• ERCP
Displacement and narrowing of main pancreatic duct adjacent to tumor
Can differentiate IPMN (which communicate with main pancreatic duct) from MCN (which do not communicate)
CT Findings
• Unilocular or multilocular encapsulated cyst in pancreatic body/tail with frequent internal septations
“Macrocystic” pattern: Few (< 6) macrocystic locules that are relatively large (> 2 cm)
• Usually of simple fluid attenuation, but may be mildly hyperdense due to hemorrhage or protein
• Frequent peripheral curvilinear calcifications or calcifications in septations (16% of cases)
• Presence of thick, irregular wall, internal mural nodularity, or thick septations suggest invasive malignancy
Upstream pancreatic ductal dilatation or atrophy suggest invasive malignancy
• No apparent communication with main pancreatic duct
In rare instances, some series have suggested possible communication with pancreatic duct in very small minority of lesions
MR Findings
• Typically show simple fluid signal (high T2; low T1), but may be slightly less T2 hyperintense due to mucin content
May show areas of T1 hyperintensity due to internal hemorrhage, proteinaceous content, or mucin
• Internal septations (typically T2 hypointense) easier to perceive on MR compared to CT
• Calcifications often not visible on MR: If visible, are low signal on all pulse sequences
• Thick, enhancing septations, wall thickening, and mural nodularity on T1WI C+ suggest invasive malignancy
• MRCP: No communication with pancreatic duct
• DWI: No role in differentiating mucinous from nonmucinous lesions or benign from malignant
Ultrasonographic Findings
• Grayscale ultrasound
Multiloculated cystic mass with echogenic internal septa
– Often associated with thick wall ± mural nodularity
Can also appear as unilocular anechoic mass
Angiographic Findings
• Conventional
Predominantly avascular mass
Cyst wall and solid component
– Show small areas of vascular blush and neovascularity
Displacement of surrounding arteries and veins by cysts
Imaging Recommendations
• CECT or MR
DIFFERENTIAL DIAGNOSIS
Pancreatic Pseudocyst
• Usually known history of pancreatitis or alcoholism ± imaging stigmata of chronic pancreatitis (pancreatic calcifications, ductal beading, etc.)
• Loculated cyst with adjacent peripancreatic fat stranding/inflammation
• Evolves over time from acute peripancreatic fluid collection into loculated pseudocyst
• Communication with pancreatic duct is frequent (70% of cases) and may be visible on ERCP or MRCP
• Lab data: Increased amylase in cyst and serum
• When occurring in pancreatic tail, may simulate unilocular mucinous cystic neoplasm
Pancreatic Serous Cystadenoma
• Well-circumscribed, lobulated cystic mass most often occurring in pancreatic head
• Classic appearance (“microcystic” or “sponge” lesion): Many small cysts separated by thin septa and with central scar demonstrating calcification
Calcification more common in serous than mucinous pancreatic neoplasms (38% vs. 16%)
• Macrocystic, oligocystic, and unilocular variants of serous cystadenoma difficult to distinguish from MCN
Thick wall and mural nodularity unusual with serous cystadenoma
Pancreatic IPMN
• Mucin-producing neoplasms which are classified into 3 types with different risks of malignancy
Side-branch IPMN: Arise in pancreatic duct side branch and carry risk of invasive malignancy of 17%
Main pancreatic duct (MPD): Arise in main pancreatic duct and carry high risk of malignancy (58%)
Combined type IPMN: Features of both side branch and main duct IPMN with prognosis similar to main duct IPMN
• Side-branch or combined type IPMN: Cyst (± nodularity, septations, calcifications) that communicates with pancreatic duct
Cystic Pancreatic Neuroendocrine Tumor
• Cystic neuroendocrine tumors more likely to be non-insulin producing and nonsyndromic
• Cystic lesion without pancreatic ductal dilatation or atrophy
Differentiate from IPMN/MCN by presence of peripheral hyperenhancement on arterial phase CECT or MR
Pancreatic Epithelial (True) Cyst
• Usually small and multiple nonenhancing cysts without pancreatic ductal dilatation
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arising from the pancreatic tail with multiple internal cystic locules and septations, some of which are thick 
. This mass was found to be a mucinous cystic neoplasm (MCN) with invasive adenocarcinoma at surgery.
arising from the upstream pancreatic body.
. MR can sometimes show complexity and suspicious features that might be difficult to identify on CT. This was found to be a MCN with low-grade dysplasia at surgery.
