Pancreas
Cystic and intraductal lesions
Squamoid cyst of pancreatic ducts
Authors: M-Nasan Abdul Baki, M.D., Michael Landau, M.D.
Editorial Board Member: Wei Chen, M.D., Ph.D.
Last staff update: 30 September 2025 (update in progress)
Copyright: 2025, PathologyOutlines.com, Inc.
PubMed Search: Squamoid cyst of pancreatic ducts
Table of Contents
Definition / general | Essential features | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Sample pathology report | Differential diagnosis | Practice question #1 | Practice answer #1 | Practice question #2 | Practice answer #2Cite this page: Abdul Baki MN, Landau M. Squamoid cyst of pancreatic ducts. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/pancreassquamoidcyst.html. Accessed October 5th, 2025.
Definition / general
- Squamoid cyst of pancreatic ducts is a rare, benign cystic lesion of the pancreas lined by flat, attenuated squamoid cells, transitional type epithelium or stratified nonkeratinizing squamous epithelium
Essential features
- Rare, benign pancreatic cyst representing cystic dilatation of native pancreatic ducts
- Lined by squamous or transitional type epithelium lacking keratinization, mucinous differentiation and cytologic atypia
- Positive for squamous markers, such as p63
- Typically discovered incidentally on imaging
- No known malignant potential
ICD coding
- ICD-10: K86.2 - cyst of pancreas
Epidemiology
- Rare, with ~33 cases reported in English literature (Ann Hepatobiliary Pancreat Surg 2021;25:293)
- Affects older adults, typically between 56 and 85 years of age (Am J Surg Pathol 2007;31:291)
- No clear gender or geographic predilection reported
Sites
- Cysts are mainly located in the pancreatic head but may also occur in the body and tail of the pancreas (Am J Surg Pathol 2007;31:291)
Pathophysiology
- Represents cystic dilatation of native pancreatic ducts, rather than de novo cyst formation, indicating an intraductal process (Am J Surg Pathol 2007;31:291)
- Centroacinar / intercalated ductal epithelium may undergo squamous transformation, possibly mediated by p63, which promotes squamous over mucinous differentiation (Am J Surg Pathol 2007;31:291)
Etiology
- No known etiology
Clinical features
- Often asymptomatic; frequently discovered incidentally during imaging for unrelated conditions (Am J Surg Pathol 2007;31:291)
Diagnosis
- Macroscopic and microscopic examination
- Immunohistochemistry
- Radiographic / endoscopic findings
Laboratory
- Cyst fluid analysis shows normal or elevated carcinoembryonic antigen (CEA) levels (Ann Hepatobiliary Pancreat Surg 2021;25:293)
Radiology description
- Well defined, unilocular or multilocular cyst, with or without septations
- Calcifications may be present
- References: Pancreas 2009;38:349, Diagn Cytopathol 2024;52:E34, Am J Surg Pathol 2007;31:291
Radiology images
Images hosted on other servers:
Abdominal ultrasound / CT scan
Prognostic factors
- Overall benign behavior (Am J Surg Pathol 2007;31:291)
Case reports
- 40 year old man with a cystic mass in the pancreatic tail (Rare Tumors 2014;6:5286)
- 51 year old woman presented with a pancreatic cystic lesion as an incidental finding on abdominal ultrasonography (Ann Hepatobiliary Pancreat Surg 2021;25:293)
- 60 year old woman with a cystic lesion in the tail of the pancreas (Korean J Hepatobiliary Pancreat Surg 2013;17:181)
Treatment
- No treatment is required for confirmed squamoid cyst of pancreatic ducts, as it is a benign lesion with no known malignant potential or risk of recurrence
- Surgical resection is typically performed only when diagnosis is uncertain, particularly to exclude mucinous or other neoplastic cystic lesions
- References: Am J Surg Pathol 2007;31:291, Ann Hepatobiliary Pancreat Surg 2021;25:293, Rare Tumors 2014;6:5286
Gross description
- Well defined, unilocular or multilocular cysts with a median size of ~1.5 cm and a relatively thin fibrotic wall (Am J Surg Pathol 2007;31:291, Ann Hepatobiliary Pancreat Surg 2021;25:293)
- Intraductal and predominantly surrounded by pancreatic tissue (Am J Surg Pathol 2007;31:291)
- Usually contain serous clear fluid with a smooth cyst lining (Am J Surg Pathol 2007;31:291, Ann Hepatobiliary Pancreat Surg 2021;25:293)
Gross images
Images hosted on other servers:
Unilocular cyst
Microscopic (histologic) description
- Cyst lining varies from flat, attenuated squamoid cells to transitional type epithelium and stratified nonkeratinizing squamous epithelium (Am J Surg Pathol 2007;31:291)
- Lining epithelium lacks keratinization, granular layer, parakeratosis and tall columnar mucinous or acinar cells (Am J Surg Pathol 2007;31:291)
- Some lesions may show oncocytic change (abundant eosinophilic granular cytoplasm with prominent nucleoli) (Arch Pathol Lab Med 2014;138:270)
- Cyst wall is composed of a thin layer of fibrous tissue (Am J Surg Pathol 2007;31:291)
- No associated lymphoid aggregates, splenic tissue, ovarian type stroma or adnexal structures are present (Am J Surg Pathol 2007;31:291)
- No significant nuclear atypia or mitosis (Ann Hepatobiliary Pancreat Surg 2021;25:293)
Microscopic (histologic) images
Contributed by Michael Landau, M.D., M-Nasan Abdul Baki, M.D. and Wei Chen M.D., Ph.D.
Multilocular cyst
Nonkeratinizing, atrophic squamous epithelium
Transitional epithelium
Cyst lining epithelium
p63 immunostain
Cytology description
- Cytology often reveals eosinophilic, acellular proteinaceous debris, which may lead to a nondiagnostic or unsatisfactory interpretation (Ann Hepatobiliary Pancreat Surg 2021;25:293)
- Nucleated mature squamous cells may be present (Diagn Cytopathol 2024;52:E34)
- Mucin, mucinous cells and malignant cells are absent (Diagn Cytopathol 2024;52:E34)
Positive stains
- p63: nuclear positivity in basal and parabasal cyst lining cells; superficial cells are typically negative
- CK7
- CK19
- MUC1 and MUC6 (60 - 70%)
- Inhibin: (80 - 90%)
- Ki67: proliferation index ranges from 1% to 7% (mean: 2.5%)
- References: Am J Surg Pathol 2007;31:291, Ann Hepatobiliary Pancreat Surg 2021;25:293
Negative stains
- CK20
- GLUT1: focally positive or negative
- References: Am J Surg Pathol 2007;31:291, Ann Hepatobiliary Pancreat Surg 2021;25:293
Sample pathology report
- Pancreas, distal pancreatectomy:
- Squamoid cyst of pancreatic ducts (see comment)
- Comment: The lesion is a unilocular cyst lined by stratified squamous type epithelium without cytologic atypia, mitotic activity or invasive features. Immunohistochemical staining demonstrates nuclear p63 positivity in the basal epithelial layers, supporting the diagnosis of a squamoid cyst of pancreatic ducts.
Differential diagnosis
- Mucinous cystic neoplasm (MCN):
- Epithelial mucinous lining with ovarian type stroma (Gut Liver 2015;9:571)
- Ovarian type stroma is positive for CD10, ER, inhibin, PR, smooth muscle actin (SMA) and vimentin (Gut Liver 2015;9:571)
- Lymphoepithelial cyst:
- Squamous, epithelial lined cyst with surrounding reactive lymphoid tissue; peripancreatic / intranodal in location (Diagnostics (Basel) 2022;13:65)
- Epidermoid cyst:
- Cyst is lined by squamous cells and is surrounded by normal splenic tissue (Acta Pathol Jpn 1991;41:916)
- Occurs exclusively in pancreatic tail
- Dermoid cyst:
- Contains adnexal elements like sebaceous glands and hair follicles (World J Surg Oncol 2007;5:85)
- Serous oligocystic adenoma:
- Cysts are lined by bland cuboidal to low columnar epithelial cells with clear cytoplasm and round, uniform nuclei featuring dense chromatin (Pathology 2002;34:148)
- Positive for inhibin and GLUT1 (Arch Pathol Lab Med 2014;138:270)
- Usually negative for squamous markers (Arch Pathol Lab Med 2014;138:270)
Practice question #1
A 62 year old woman underwent resection of a 2.1 cm cystic lesion in the pancreatic body. Histologic examination reveals a multilocular cyst lined by bland squamoid epithelium without mucinous differentiation or keratinization. Which of the following statements regarding squamoid cysts of pancreatic ducts is true?
- Basal epithelial cells typically show nuclear p63 positivity
- Cyst wall frequently contains lymphoid aggregates and splenic tissue
- It exhibits mucinous differentiation with keratin pearl formation
- It is considered a premalignant pancreatic cystic neoplasm
Practice answer #1
A. Basal epithelial cells typically show nuclear p63 positivity. Squamoid cyst of pancreatic ducts is positive for squamous markers, such as p63. The p63 shows nuclear positivity in basal and parabasal cyst lining cells; superficial cells are typically negative. Answer B is incorrect because squamoid cyst of pancreatic ducts lacks associated lymphoid aggregates, splenic tissue, ovarian type stroma or adnexal structures. Answer C is incorrect because the epithelium of squamoid cysts of pancreatic ducts lacks both mucinous differentiation and keratinization; keratin pearls are not a feature. Answer D is incorrect because squamoid cyst of pancreatic ducts is a benign lesion with no known malignant potential.
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Reference: Squamoid cyst of pancreatic ducts
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Reference: Squamoid cyst of pancreatic ducts
Practice question #2
Which of the following is most consistent with the immunohistochemical profile of squamoid cysts of pancreatic ducts?
- Positive for CK20 and chromogranin
- Positive for MUC2 and MUC5AC
- Positive for p63, CK7 and CK19
- Positive for TTF1 and inhibin
Practice answer #2
C. Positive for p63, CK7 and CK19. Squamoid cyst of pancreatic ducts is positive for nuclear p63 in basal epithelial layers, CK7 and CK19. Answers A, B and D are incorrect because squamoid cyst of pancreatic ducts is usually negative for CK20, chromogranin, MUC2, MUC5AC, TTF1 and inhibin.
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