Definition/General
Introduction:
Pancreatic pseudocyst is a fluid collection without epithelial lining
Develops as complication of acute pancreatitis
Contains pancreatic enzymes and inflammatory debris
Most common pancreatic cystic lesion
FNAC shows characteristic paucicellular findings.
Origin:
Results from pancreatic duct disruption following acute pancreatitis
Enzymatic digestion creates cavity
Fibrous wall formation occurs over time
Contains pancreatic juice and inflammatory material
No true epithelial lining present.
Classification:
Acute pseudocyst (<4 weeks duration)
Chronic pseudocyst (>4 weeks duration)
Organized pseudocyst with thick wall
Complicated pseudocyst (infected, hemorrhagic)
Multiple pseudocysts possible.
Epidemiology:
Complicates 10-15% of acute pancreatitis cases
Male predominance (M:F = 3:1)
Peak incidence 4th-5th decades
Alcohol-related pancreatitis most common cause
More common in developing countries.
Clinical Features
Presentation:
Persistent abdominal pain after acute pancreatitis
Palpable mass (large pseudocysts)
Nausea and vomiting
Early satiety
Weight loss
Biliary obstruction (head pseudocysts).
Symptoms:
Epigastric pain (most common)
Post-prandial fullness
Nausea and vomiting
Palpable abdominal mass
Jaundice (ductal compression)
Fever (if infected)
Gastric outlet obstruction.
Risk Factors:
Acute pancreatitis (any etiology)
Alcohol abuse
Gallstone pancreatitis
Pancreatic trauma
Previous pancreatic surgery
Chronic pancreatitis.
Screening:
CT scan (diagnostic imaging)
MRI/MRCP for detailed evaluation
EUS for cyst characteristics
Serum amylase/lipase may be elevated
Cyst fluid analysis confirmatory.
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Gross Description
Appearance:
Unilocular cystic lesion without solid components
Thick fibrous wall (mature pseudocyst)
Contains turbid, brownish fluid
No papillary projections
Smooth internal surface.
Characteristics:
Round to oval cystic lesion
Thick fibrous capsule
No epithelial lining
Contains pancreatic juice
Debris and inflammatory material
May have calcifications in wall.
Size Location:
Size ranges from 2-20 cm (average 6-8 cm)
Body and tail most common locations (60%)
Head involvement in 30%
May involve peripancreatic tissues
Lesser sac location common.
Multifocality:
Multiple pseudocysts in 20-30% cases
Usually related to severe acute pancreatitis
May communicate with pancreatic duct
Satellite pseudocysts around main lesion.
Microscopic Description
Histological Features:
Fibrous wall without epithelial lining
Chronic inflammatory infiltrate
Granulation tissue formation
Vascular proliferation
Hemosiderin deposits
Calcifications in chronic cases.
Cellular Characteristics:
Fibroblasts and myofibroblasts predominant in wall
Chronic inflammatory cells
Macrophages with debris
Endothelial proliferation
No epithelial cells lining cavity.
Architectural Patterns:
Cystic cavity lined by fibrous tissue
Inflammatory granulation tissue
Organized fibrous capsule
Vascular ingrowth
No true epithelial lining present.
Grading Criteria:
Acute vs chronic based on wall maturation
Complicated vs uncomplicated
Organized vs unorganized
Infected vs sterile
Size-based classification.
Immunohistochemistry
Positive Markers:
Smooth muscle actin (myofibroblasts in wall)
CD68 (macrophages)
Vimentin (fibroblasts)
CD31/CD34 (vascular proliferation)
Trichrome stain (fibrosis).
Negative Markers:
Cytokeratins (no epithelial lining)
CEA (helps exclude mucinous cysts)
Chromogranin A (no neuroendocrine cells)
Mucin stains negative.
Diagnostic Utility:
Absence of epithelial markers confirms pseudocyst
CEA levels in cyst fluid typically low (<192 ng/ml)
Helps distinguish from mucinous neoplasms
Inflammatory markers present.
Molecular Subtypes:
No molecular subtypes recognized
Inflammatory etiology determines characteristics
Time-dependent changes in wall organization
Associated with underlying pancreatitis type.
Molecular/Genetic
Genetic Mutations:
No specific genetic mutations
Reflects underlying pancreatitis etiology
Inflammatory pathway activation
Fibrosis-related gene expression
No oncogenic mutations.
Molecular Markers:
Inflammatory cytokines elevated in cyst fluid
High amylase levels (>250 U/L)
High lipase levels
Protein content variable
Low viscosity fluid.
Prognostic Significance:
Size >6 cm less likely to resolve spontaneously
Thick wall indicates chronicity
Communication with duct affects resolution
Location impacts complications.
Therapeutic Targets:
Percutaneous drainage for large/symptomatic cysts
Endoscopic drainage (transmural or transpapillary)
Surgical drainage (cystoenterostomy)
Conservative management for small asymptomatic cysts.
Differential Diagnosis
Similar Entities:
Mucinous cystic neoplasm
Intraductal papillary mucinous neoplasm (IPMN)
Serous cystadenoma
Cystic pancreatic neuroendocrine tumor
Retention cyst.
Distinguishing Features:
Pseudocyst: No epithelial lining
Pseudocyst: High amylase/lipase
Pseudocyst: History of pancreatitis
MCN: Epithelial lining present
MCN: Ovarian-type stroma
IPMN: Ductal communication.
Diagnostic Challenges:
Cystic degeneration of solid tumors
Infected pseudocyst vs cystic neoplasm
Sampling adequacy in FNAC
May need cyst fluid analysis
Clinical history crucial.
Rare Variants:
Hemorrhagic pseudocyst
Infected pseudocyst
Pseudocyst with solid debris
Multiloculated pseudocyst
Extrapancreatic extension.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
FNAC from pancreatic cystic lesion, [location]
Adequacy
Specimen is adequate for evaluation
Fluid Characteristics
[Volume] ml of [color/consistency] fluid obtained
Cellular Findings
Paucicellular specimen with [inflammatory cells/debris]
Epithelial Cells
No epithelial cells identified
Background
Background shows [proteinaceous debris/inflammatory cells]
Cyst Fluid Analysis
Amylase: [level] U/L, CEA: [level] ng/ml
Final Diagnosis
FNAC pancreatic cyst: Findings consistent with pseudocyst