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Pancreas

Exocrine tumors

Mucinous cystic neoplasm (MCN)


Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 9 July 2014, last major update August 2012
Copyright: (c) 2001-2014, PathologyOutlines.com, Inc.

General
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● Benign or potentially low grade malignant cystic epithelial neoplasm composed of cells which contain intracytoplasmic mucin (WHO)
● One of three precursor lesions of pancreatic adenocarcinoma (also PanIN, IPMN)
● WHO Classification: with low- or intermediate-grade dysplasia, with high-grade dysplasia or with an associated invasive carcinoma

Clinical features
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● Almost always women, mean age 45 years
● Abdominal pain or mass
● < 20% associated with invasive carcinoma
● Metastases usually restricted to abdominal cavity; metastases to ovary may simulate primary ovarian tumors
● Can also occur in the liver
● Rarely associated with anaplastic carcinoma (World J Gastroenterol 2008;14:132, Arch Pathol Lab Med 1997;121:1104), or sarcomatous stroma with aggressive behavior

Case reports
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● 65 year old man (JOP 2012;13:687)

Gross description
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● Large (mean 10 cm)
● Usually in body/tail, multilocular (occasionally unilocular) megacysts that donít communicate with ductal system unless fistula are present
● Cyst wall is papillary, trabecular or thickened
● Has mucoid/watery cyst contents
● Must sample solid areas within the cyst

Gross images
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Unilocular cyst filled with gelatinous material; cyst on left is hemorrhagic


Conspicuous, irregular, solid protuberances projecting into cystic cavities


Invasive tumor from tail of pancreas in 36 year old woman shows large cyst with solid tumor


Multiloculated cystic lesion


39 year old man with multilocular cyst with thick mucin

Micro description
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● Lined by tall mucin-producing cells, often forming papillae
● Intestinal or gastric foveolar-type features
● Calcification common
● Ovarian type stroma is relatively specific; recapitulates fetal pancreatic mesenchyme around ducts (ER+, PR+, inhibin+)
● May have mural nodules with features of giant cell tumor, MFH or anaplastic carcinoma
● Endocrine cells often scattered among columnar lining cells
Note: must sample extensively to rule out an invasive component (Am J Surg Pathol 1999;23:1320)

Micro images
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Various images


Adenoma


Cyst wall containing lobular glands with benign histology


Cyst wall with focal hyalinization and calcification in cellular stroma


Foreign body reaction


Squamous metaplasia

Dysplasia:


Low grade dysplasia


Intermediate grade dysplasia


High grade dysplasia

Invasive disease:

Invasion: lining epithelium is desquamated (top)


Invasion: cribriform architecture and moderate nuclear atypia


36 year old woman


Sarcomatous stroma

Immunostains:

Scattered endocrine cells are serotonin+


Squamous metaplasia

Positive stains
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● MUC5AC, DPC4 present in in-situ areas (usually lost in invasive disease, Am J Surg Pathol 2000;24:1544)
● Ovarian type stroma is ER+, PR+, inhibin+, CD10+
● p53, EGFR, cathepsin E (CTSE ), MET (encoding hepatocyte growth factor binding receptor), MYC, PSCA, S100P in epithelium, steroidogenic acute regulatory protein (STAR), LCK

Negative stains
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● MUC1 (except in invasive components, Am J Surg Pathol 2002;26:466), MUC2 (except for faint staining of goblet cells)

Molecular description
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● Molecular analysis suggests monoclonal origin with subsequent divergence for cases with sarcomatous stroma (Mod Pathol 2000;13:86, Am J Surg Pathol 1997;21:70)
● Kras mutations noted in in-situ or invasive areas, inactivating SMAD4 and TP53 mutations in more advanced MCNs
● Cyst fluid analysis: higher expression of microRNAs in mucinous precursors, low amylase levels

Differential diagnosis
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IPMN: usually head, communicates with duct system
Ovarian mucinous tumors: similar clinical and histologic appearance
Pancreatic pseudocyst: mimics MCN when MCN has denuded cyst lining; MCN cystic fluid has high CEA content and viscosity, high expression of microRNAs, lower amylase and elastase I than pseudocyst, although values may vary within different loculi of same neoplasm (Am J Clin Pathol 1993;100:425)
Pancreatic ductal adenocarcinoma, cystic

End of Pancreas > Exocrine tumors > Mucinous cystic neoplasm (MCN)


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