Pancreas
Exocrine tumors / carcinomas
Mucinous cystic neoplasm (MCN)

Author: Enoch Kuo, M.D.
Editor: Raul S. Gonzalez, M.D.

Revised: 4 April 2018, last major update March 2018

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Mucinous cystic neoplasm[TI] pancreas

Cite this page: Kuo, E. Mucinous cystic neoplasm (MCN). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/pancreasmcn.html. Accessed June 21st, 2018.
Definition / general
  • Benign or potentially low grade malignant cystic epithelial neoplasm composed of cells which contain intracytoplasmic mucin (IARC: 8470 / 0 Mucinous Cystoma [Accessed 21 March 2018])
  • WHO Classification:
    • MCN with low grade dysplasia (adenoma)
    • MCN with moderate dysplasia (borderline neoplasm)
    • MCN with high grade dysplasia (carcinoma in situ)
    • MCN with invasive carcinoma
Essential features
  • Cystic neoplastic lesion that is a precursor to pancreatic adenocarcinoma
  • May harbor invasive carcinoma
ICD-10 coding
  • C25 : malignant neoplasm of pancreas (if malignant)
  • D13.6 : benign neoplasm of pancreas (if benign)
Epidemiology
Sites
  • Distal pancreas (> 95%) (Ann Surg 2008;247:571)
  • Can also occur in the liver and gallbladder
  • Metastases usually restricted to abdominal cavity; metastases to ovary may simulate primary ovarian tumors
Pathophysiology
  • Ectopic ovarian stroma is thought to be seeded from primordial ovarian cells at early stages of embryonic development and cysts are later formed by hormones and growth factors released by the ovarian stroma (Am J Surg Pathol 1999;23:410)
Etiology
  • No known etiology
Clinical features
Diagnosis
  • Cytology and lab analysis of pancreatic cyst fluid from endoscopic ultrasound guided FNA
  • Histology of pancreatic resection
Laboratory
  • Elevated CEA and presence of KRAS mutation in cyst fluid supports a mucinous cyst (includes MCN and IPMN) (Ann Gastroenterol;26:122)
Radiology description
  • Thick walled, single, septated cyst in the body or tail of the pancreas (Gut Liver 2015;9:571)
  • May have nodules or calcifications
Prognostic factors
Case reports
Treatment
Gross description
  • Large (mean 10 cm)
  • Typically unilocular megacysts that do not communicate with ductal system, though up to 15% communicate with main pancreatic duct (Gut Liver 2015;9:571)
  • Cyst wall is papillary, trabecular or thickened
  • Has mucoid / watery cyst contents
  • Must sample solid areas within the cyst
Gross images

Images hosted on PathOut server:
Contributed by
Dr. Diana Agostini-Vulaj

MCN with no connection to main duct


AFIP Images

Unilocular cyst

Conspicuous, irregular, solid protuberances

Multiloculated cystic lesion

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



Images hosted on other servers:

39 year old man with multilocular cyst with thick mucin

Microscopic (histologic) description
  • Large cyst lined by intestinal, pseudopyloric or gastric foveolar type epithelium that often form papillae, surrounded by characteristic dense ovarian type stroma (Gut Liver 2015;9:571)
  • Epithelial lining has variable atypia (none, low grade, high grade); scattered neuroendocrine cells may be present
  • Invasive adenocarcinoma may or may not be present (Gut Liver 2015;9:571); must sample extensively to rule out an invasive component (Am J Surg Pathol 1999;23:1320)
  • Calcifications are common
  • May have mural nodules with features of giant cell tumor, MFH or anaplastic carcinoma
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Raul S. Gonzalez, M.D.

MCN with invasion




AFIP Images

Adenoma

Cyst wall containing lobular glands

Cyst wall with focal hyalinization

Low grade dysplasia


Foreign body reaction

Intermediate grade dysplasia

High grade dysplasia


Invasion: lining epithelium is desquamated

Invasion: cribriform architecture

36 year old woman

Scattered endocrine cells are serotonin+



Images hosted on other servers:

Mucinous cystic neoplasm

Low grade dysplasia

Squamous metaplasia

Cytology description
  • Cyst aspirates are usually acellular with thick, gelatinous mucus
  • Clusters of 3 dimensional atypical glandular cells with hyperchromasia predict at least moderate dysplasia (Arch Pathol Lab Med 2009;133:388)
Positive stains
Negative stains
Molecular / cytogenetics description
  • KRAS mutations noted in in situ or invasive areas, inactivating SMAD4 and TP53 mutations in more advanced MCNs (Gut Liver 2015;9:571)
  • Negative for GNAS mutations
Differential diagnosis
Board review question #1
Which of the following findings on fine needle aspiration of a pancreatic cyst are most consistent with a mucinous cystic neoplasm?

  1. Decreased CEA, decreased amylase, no KRAS mutation, no GNAS mutation
  2. Elevated CEA, elevated amylase, KRAS mutation, GNAS mutated
  3. Elevated CEA, highly elevated amylase, no KRAS mutation, no GNAS mutation
  4. Elevated CEA, variable amylase, KRAS mutation, no GNAS mutation
Board review answer #1
D. Mucinous Cystic neoplasms have elevated CEA, variable amylase, KRAS mutation and no GNAS mutation.
If a GNAS mutation is present, then the findings will favor an IPMN (Answer B).
Decreased CEA and amylase with no KRAS or GNAS mutations favor a serous cystadenoma.
An elevated CEA and amylase without KRAS or GNAS mutations will favor a pancreatic pseudocyst (Answer C).