What are the inclusion criteria for Endoscopic Ultrasonography (EUS)-guided Fine Needle Aspiration Cytology (FNAC) and Fine Needle Aspiration Biopsy (FNAB) study?

Inclusion Criteria for EUS-Guided FNAC and FNAB Studies

EUS-guided fine needle aspiration cytology (FNAC) and biopsy (FNAB) should be performed for pancreatic cysts ≥2.5 cm with at least one worrisome feature, any cyst ≥3 cm regardless of other features, pancreatic ductal dilation 5-9 mm, solid pancreatic masses of any size, and subepithelial gastrointestinal lesions when forceps biopsies are non-diagnostic. 1, 2

Pancreatic Cystic Lesions

Size-Based Criteria

• Cysts ≥3 cm: EUS-FNA is indicated even without other worrisome features, as this size alone confers a 3-fold increased risk of cyst-related malignancy 1
• Cysts ≥2.5 cm with ≥1 worrisome feature: This threshold recognizes that cysts slightly below 3 cm may possess worrisome features and still contain sufficient fluid for analysis 1
• Minimum cyst size ≥1.7 cm: This represents the minimum volume needed to perform cytology and biomarker analysis (CEA and amylase levels) 1, 2

Worrisome Features Triggering EUS-FNA

• Solid component within the cyst: Increases malignancy risk up to 8-fold 1
• Enhancing mural nodule or thick septation: Detected on contrast-enhanced imaging 1
• Main pancreatic ductal dilation 5-9 mm: Associated with 57-92% malignancy risk for main duct IPMN 1
• Abrupt caliber change in pancreatic duct with distal pancreatic atrophy: Suggests main duct involvement 1

High-Risk Stigmata (Absolute Indications)

• Main pancreatic duct dilation ≥10 mm: Should prompt surgical referral rather than EUS-FNA alone 1
• Obstructive jaundice in a patient with cystic lesion of the pancreatic head: Indicates high-risk disease 1

Solid Pancreatic Masses

Universal Inclusion Criteria

• Any solid pancreatic mass regardless of size: Diagnostic accuracy reaches 92-95% for these lesions 2, 3
• Mean tumor size in studies: 3.3 cm (range 1.3-7 cm), but smaller lesions are also appropriate candidates 3
• Location: Head (65%), uncinate (12%), body (17%), tail (6%) - all locations are appropriate for EUS-FNA 3

Special Considerations for Small Lesions

• Lesions ≤10 mm: Technical success rate is 80.8% with sensitivity of 82.3%, but these remain appropriate candidates when PDAC is suspected 4
• Failed or negative EUS-FNAB in lesions ≤10 mm: Consider salvage pancreatic juice cytology, which correctly diagnoses 74.3% of cases missed by EUS-FNAB 4

Repeat Procedures

• Prior non-diagnostic EUS-FNA with persistent clinical suspicion: Repeat EUS-FNA yields correct diagnosis in 61-84% of cases 2, 3
• Atypical or suspicious cytology: These patients deserve further clinical evaluation, as nearly all such cases are subsequently confirmed malignant 3

Subepithelial Gastrointestinal Lesions

Primary Indications

• Indeterminate subepithelial lesions when forceps biopsies are non-diagnostic: EUS-FNA/FNB serves as the definitive tissue acquisition method 2
• Lesions arising from third or fourth echo layer: To differentiate GISTs from leiomyomas and assess malignant potential 2

Size-Dependent Accuracy

• Lesions <2 cm: 71% diagnostic accuracy 2
• Lesions 2-4 cm: 86% diagnostic accuracy 2
• Lesions >4-5 cm: 95-100% diagnostic accuracy 2

Lymphadenopathy

Anatomic Locations

• Mediastinal nodes: Particularly sub-carinal and aortopulmonary window locations 5
• Celiac and peripancreatic nodes: For staging of pancreatic and gastric malignancies 5
• Retroperitoneal lymphadenopathy: When accessible by echoendoscope 5

Diagnostic Yield

• Tuberculosis vs. malignancy differentiation: Major indication, with tuberculosis diagnosed in 26/67 (38.8%) and malignancy in 23/67 (34.3%) of lymph node FNACs 5

Biliary Lesions

Specific Indications

• Distal biliary lesions: EUS-FNA demonstrates 81% sensitivity (superior to 59% for proximal lesions) 2
• Suspected malignant biliary obstruction with negative or equivocal CT/MRI: EUS with FNA provides both imaging and cytologic diagnosis 1

Technical Feasibility Requirements

Procedural Considerations

• Lesions accessible by echoendoscope: Must be within reach of the linear or radial scope 2, 6
• Adequate needle passes: Median of 4 passes (range 1-11) typically performed, with average of 5 passes (range 3-9) in most studies 3, 7
• On-site cytopathologist availability: Improves specimen adequacy assessment and reduces non-diagnostic rates to 2-10% 3, 7

Needle Selection

• 22-gauge and 25-gauge needles: More maneuverable and favorable for most positions 2
• 19-gauge needles: Optimal for cyst aspirations but difficult to maneuver in fundus and duodenum 2
• Fine-needle biopsy (FNB) needles: Demonstrate superior tissue acquisition (75-100% accuracy) compared to FNA needles 2

Exclusion Criteria (Contraindications)

Absolute Contraindications

• Patients too ill to undergo procedure safely: Hypoxemic or hypotensive patients 5
• Complete esophageal blockage at upper end by tumor: Not allowing scope/EUS probe to advance beyond 5
• Uncorrectable coagulopathy: Standard endoscopic contraindications apply 2

Relative Contraindications

• Cystic lesions without prophylactic antibiotics: Must administer antibiotics and continue for up to 48 hours to prevent infection 2
• Intervening vascular structures: Increases risk of hemorrhage 2

Clinical Context Modifying Inclusion

High-Risk Clinical Features

• High clinical suspicion for malignancy with non-diagnostic imaging: Warrants EUS-FNA even for smaller or less concerning lesions 2
• Potentially resectable lesions requiring preoperative tissue confirmation: Necessary for treatment planning 2
• Staging requirements: For known malignancies requiring lymph node assessment 5

Common Pitfalls to Avoid

• Do not defer EUS-FNA for cysts ≥3 cm waiting for additional worrisome features to develop: Size alone is sufficient indication given the dismal survival rate for pancreatic carcinoma and potential benefit of early dysplasia detection 1
• Do not rely solely on imaging for pancreatic cysts with worrisome features: Addition of EUS-FNA to diagnostic algorithms alters management in 72% of patients and reduces unnecessary surgeries by 91% 1
• Do not abandon diagnosis after single non-diagnostic EUS-FNA: Repeat procedures have 61-84% success rate when clinical suspicion remains high 2, 3
• Do not interpret "atypical" or "suspicious" cytology as benign: Nearly all such cases are subsequently confirmed malignant, with sampling error accounting for 80% of indeterminate results 3
• Do not perform EUS-FNA on cysts <1.7 cm: Insufficient fluid volume for adequate cytology and biomarker analysis 1, 2