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Pancreas

Tumors

Colloid (mucinous noncystic) carcinoma


Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 30 November 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Also called pure mucinous or gelatinous carcinoma
● Infiltrating ductal epithelial neoplasm characterized by large extracellular stromal mucin pools containing suspended neoplastic cells in at least 80% of neoplasm; almost always arise in association with intestinal-type IPMN; large mucin pools partially lined by well-differentiated cuboidal to columnar neoplastic cells with clumps or strands of neoplastic cells, possibly floating signet-ring cells (WHO)
● Muconodular invasive component of 1 cm or more
● Mucin tends to be retained during histologic processing

Pathophysiology
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● Inverse polarization of cells (mucin glycoproteins in stroma-facing surfaces vs. luminal surface or diffuse in usual ductal adenocarcinoma), lack of external lamina or basement membrane, and expression of MUC2 (gel forming mucin) (rare in UDA) may cause accumulation of extracellular mucin, which contains tumor spread and appears to have tumor suppressor activity (Am J Surg Pathol 2003;27:571, Mod Pathol 2002;15:1087)

Prognostic factors and survival
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● 5 year survival 57% (vs. 5% for usual ductal carcinoma)
● Long survival even with nodal metastases, perineurial invasion, vascular invasion, but see Am J Surg Pathol 2002;26:56 (similar survival to usual ductal carcinoma using 50% as the minimal required colloid component)
● All patient deaths in one study were associated with surgical incision into the tumor or core biopsy - incisional biopsy may contribute to thromboembolism or tumor dissemination (Am J Surg Pathol 2001;25:26)

Clinical features
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● Mean age 61; M=F, usually in head of pancreas
● Associated with IPMN (almost always arise in association with an intestinal-type IPMN), ampullary/duodenal tubulovillous adenomas, mucinous cystic neoplasm
● Compared to UDA, are larger (5.5 cm), lower stage, better survival

Case reports
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● 52 year old woman with history of necrotizing pancreatitis (Arch Pathol Lab Med 2005;129:255)
● 64 year old man with 15 cm tumor (JOP 2012;13:219)

Gross description
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● Soft, mean 5 cm

Gross images
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Large, well-demarcated, associated with intestinal-type IPMN


Whipple resection specimen shows a well-demarcated tumor in the head of the pancreas with a nodular pattern and a gelatinous cut surface. The probe indicates the pancreatic duct which runs into the minor papilla

Micro description
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● Most of tumor consists of mucin lakes containing rare tumor cells
● Tumor cells are highly atypical and in cribriform/stellate clusters, signet-ring cells (not in stroma), small tubules
● Tumor cells may also line the mucin lakes
● Perineurial invasion and regional nodal metastases common
● Usually arise in association with IPMN or tubular/tubulovillous adenoma

Micro images
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Large mucin pools are partially lined by well-differentiated cuboidal to columnar neoplastic cells and contain clumps or strands of neoplastic cells


MUC2+

Cytology description
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● Difficult to spread thinly on slides due to abundant mucus
● Malignant cells may be rare

Cytology images
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Figure 1: abundant mucinous material, degenerated inflammatory cells, rare 3D fragments of benign-appearing epithelium
Figure 2: cytologic atypia with enlarged, crowded, hyperchromatic nuclei
Figure 3: numerous single cells with large solitary intracytoplasmic vacuoles consistent with mucin


Positive stains
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● MUC2+ (marker of indolent mucin, UDA usually MUC2-), CEA, CDX2

Negative stains
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● MUC1

Molecular description
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● Kras mutations (33%), p53 (22%)
● Microsatellite stable unlike mucinous carcinomas of colon (Mod Pathol 2003;16:537)

Electron microscopy description
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● Mucigen granules on stromal surface, no basement membrane

Differential diagnosis
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Ductal adenocarcinoma of usual type: some mucin but no mucin lakes
IPMN: smooth contours, clusters of epithelium, mucin lost in processing
Mucinous cystic neoplasms: cystic spaces lined by mucinous epithelium, ovarian type stroma, usually women, no association with IPMN

End of Pancreas > Tumors > Colloid (mucinous noncystic) carcinoma


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