Pancreas
Cysts
Simple mucinous cyst


Topic Completed: 29 June 2020

Minor changes: 3 August 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Mucinous nonneoplastic cyst pancreas

Amanda Kitson, M.D.
Jiaqi Shi, M.D., Ph.D.
Page views in 2019: 1,674
Page views in 2020 to date: 1,242
Cite this page: Kitson A, Shi J. Simple mucinous cyst. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/pancreasmucnoncyst.html. Accessed August 15th, 2020.
Definition / general
  • Mucinous pancreatic cyst with minimal cytologic atypia, grossly > 1 cm, lined by single layer of gastric type flat epithelium without ovarian type stroma
Essential features
  • Unilocular or multilocular mucinous cyst (> 1 cm) with single layer of columnar or cuboidal cells and low grade dysplasia
  • Paucicellular fibrotic wall with no ovarian type stroma or lymphoid band
  • Cyst rarely communicates with pancreatic duct
  • High cyst fluid CEA, low amylase
  • KRAS and KMT2C mutations in a subset of cases
  • Follows benign clinical course, no reported progression to carcinoma
Terminology
ICD coding
  • ICD-10: K86.2 - cyst of pancreas
Epidemiology
Sites
Clinical features
Diagnosis
Laboratory
Radiology description
  • CT / MRI:
  • EUS:
    • Septate in 26.3%, solid component in 10.5%, possible communication with pancreatic duct in 21% (Pancreas 2012;41:813)
Radiology images

Contributed by Amanda Kitson, M.D. and Jiaqi Shi, M.D., Ph.D.

CT: abdomen coronal

CT abdomen, transverse section

T2 MRI: abdomen coronal

Prognostic factors
Case reports
Treatment
  • Often treated with surgical resection due to preoperative imaging indistinguishable from other mucinous neoplasms
  • Surveillance
Clinical images

Images hosted on other servers:

Abnormal upper GI endoscopy

Hematochezia and active bleeding from ampulla

Pancreatic cyst and elevated posterior wall of gastric body

Gross description
Gross images

Contributed by Amanda Kitson, M.D. and Jiaqi Shi, M.D., Ph.D.
Multiloculated cyst in pancreatic head

Multiloculated cyst in pancreatic head

Cyst in pancreatic body

Cyst in pancreatic body

Frozen section description
  • > 1 cm unilocular or multilocular cyst
  • Flat gastric type mucinous epithelium
  • No significant atypia
  • No ovarian type stroma
Frozen section images

Contributed by Amanda Kitson, M.D. and Jiaqi Shi, M.D., Ph.D.
Monolayer of mucinous epithelium

Monolayer of mucinous epithelium

Epithelium with minimal atypia

Epithelium with minimal atypia

Fibrotic cyst wall

Fibrotic cyst wall

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Amanda Kitson, M.D. and Jiaqi Shi, M.D., Ph.D.
Cuboidal to columnar epithelium

Cuboidal to columnar epithelium

Gastric type mucinous epithelium

Gastric type mucinous epithelium

Hypocellular stroma

Hypocellular stroma

Focal atypia

Focal atypia

Virtual slides

Images hosted on other servers:

Cyst and uninvolved pancreas

Fibrotic cyst wall

Frozen section, mucinous cyst

Columnar lining, focal atypia

Focal papillary excrescences

Cytology description
  • Flat honeycomb sheets / nests of cuboidal or columnar cells without significant atypia (100%) (Pancreas 2013;42:27, Pancreas 2012;41:813)
  • Round to oval nuclei, small to slightly enlarged, 1 - 2 inconspicuous nucleoli, fine granular chromatin, smooth nuclear contour, nuclear grooves (43.5%), nuclear pseudoinclusions (26.1%) (Pancreas 2013;42:27)
  • Delicate, vacuolated cytoplasm (60.9%), variable in amount (Pancreas 2013;42:27)
  • May show papillary architecture (10.5%), acini formation (10.5%), 3D clusters (5.3%), single cell pattern (5.3%), goblet cells (17.4%) (Pancreas 2013;42:27)
  • Background mucin, macrophages (43.5%), rarely stroma (17.4%) (Pancreas 2013;42:27)
  • Limitations: may not be representative of entire cyst lining
Cytology images
  • Unremarkable mucin
Positive stains
Molecular / cytogenetics description
Sample pathology report
  • Pancreas, resection:
    • Simple mucinous cyst (see comment)
    • Comment: Many of these lesions have KRAS mutation. Although there is no consensus, many authors consider this entity a neoplastic process. However, they tend to have a benign behavior with no reported recurrence or malignant transformation after resection.
Differential diagnosis
  • Metaplastic squamous / transitional epithelium (Clin Endosc 2015;48:31)
  • Board review style question #1

      A 62 year old woman presents with an incidental cystic lesion in the head / uncinate process of the pancreas on imaging. The cyst does not communicate with the pancreatic duct. Upon grossing of the Whipple resection specimen, a 4.6 cm multiloculated cyst with smooth lining is present in the head / uncinate. Representative H&E image of the cyst lining is shown. Which of the following is true regarding this entity?

    1. High grade dysplasia is often present
    2. KRAS mutations have been demonstrated in a subset of cases
    3. Often communicate with pancreatic duct
    4. Ovarian type stroma is diagnostic of this entity
    5. Papillary architecture is common
    Board review answer #1
    B. KRAS mutations have been demonstrated in a subset of cases

    Reference: Simple mucinous cyst

    Comment Here
    Board review style question #2
      A 2.3 cm multiloculated cyst with smooth lining located in the head of the pancreas was removed during surgery. It does not connect with the main pancreatic duct. The pathologist observes that the cyst lining is composed of a single layer of columnar mucinous cells with no papillary architecture or high grade dysplasia. The surrounding cyst wall is fibrotic and paucicellular with no ovarian type stroma. No ductal obstruction is present. What is the best diagnosis for this entity?

    1. Intraductal pancreatic mucinous neoplasm
    2. Mucinous cystic neoplasm
    3. Pancreatic pseudocyst
    4. Retention cyst
    5. Simple mucinous cyst
    Board review answer #2
    E. Simple mucinous cyst

    Reference: Simple mucinous cyst

    Comment Here
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