What are the types of gallbladder polyps?

Types of Gallbladder Polyps

Gallbladder polyps can be broadly categorized into two main types: nonneoplastic polyps and neoplastic polyps, with the majority being benign nonneoplastic lesions. 1

Nonneoplastic Polyps

• Cholesterol polyps: Account for approximately 60% of all gallbladder polyps, typically small (<10mm) with negligible risk of malignant transformation 1, 2
• Inflammatory polyps: Develop in response to chronic inflammation of the gallbladder wall 2
• Adenomyomatosis: The second most common benign polypoid lesion (25% of cases), characterized by hyperplasia of the gallbladder wall with Rokitansky-Aschoff sinuses 2, 1

Neoplastic Polyps

• Intracholecystic papillary neoplasms (ICPNs): Mass-forming, noninvasive epithelial neoplasms ≥10mm that project into the gallbladder lumen 1
  • Four morphologic patterns: biliary, gastric, intestinal, and oncocytic 1
  • May have low-grade or high-grade epithelial dysplasia 1
• Pyloric gland adenomas: Smooth-surfaced polypoid lesions composed of tightly packed glands with pyloric-type low cuboidal epithelium 1
  • Occur in 0.2%-0.5% of cholecystectomy specimens 1
  • May be associated with familial adenomatous polyposis or Peutz-Jeghers syndrome 1
• Adenocarcinoma: Primary malignant tumor that may develop from neoplastic polyps 2, 3

Morphologic Classification

Based on their appearance, gallbladder polyps can be classified into three risk categories 1:

• Extremely low risk polyps: Pedunculated with a "ball-on-the-wall" configuration or thin stalk 1, 4
• Low risk polyps: Pedunculated with a thick or wide stalk or sessile configuration 1, 4
• Indeterminate risk polyps: Have focal wall thickening adjacent to the polyp 1, 4

Epidemiology and Clinical Significance

• Gallbladder polyps affect approximately 5% of the adult population 5
• Only about 6% of all gallbladder polyps are neoplastic 1
• The risk of malignant transformation from polypoid lesions ranges from 0-27% in the literature 2
• Neoplastic polyps are typically larger (mean size 18-21mm) than nonneoplastic polyps (mean size 4-7.5mm) 1

Diagnostic Features

• On ultrasound, cholesterol polyps typically appear as small, non-mobile, non-shadowing lesions attached to the gallbladder wall 6
• Cholesterol polyps may show stalk-like central enhancement on contrast-enhanced ultrasound (CEUS) 6, 4
• MRI may show high T1-weighted signal in cholesterol polyps 6

Risk Factors for Malignancy

• Size ≥10mm is the strongest predictor of malignancy 4, 7, 3
• Sessile morphology increases risk of malignancy 4
• Rapid growth (≥4mm within 12 months) is concerning for malignancy 4
• Focal wall thickening adjacent to polyp suggests higher risk 4
• Age >50 years is associated with higher risk of malignancy 3
• Single polyps are more likely to be malignant than multiple polyps 3

Management Considerations

• Symptomatic polyps generally warrant cholecystectomy regardless of size 3
• Asymptomatic polyps ≥10mm typically require surgical removal 4, 7
• Polyps 6-10mm generally require follow-up ultrasound, though frequency and duration are not firmly established 7
• Pedunculated polyps <5mm generally do not require follow-up 7
• Patients with primary sclerosing cholangitis have significantly higher risk (18-50%) of malignancy in gallbladder polyps, with consideration for cholecystectomy at a lower threshold of ≥8mm 4