What causes the formation of liver polyps?

Formation of Liver Polyps

Liver polyps do not exist as a distinct clinical entity—the term "liver polyps" is a misnomer that likely refers to either gallbladder polyps, biliary hamartomas (Von Meyenburg complexes), or other hepatic lesions that may appear polypoid on imaging.

Clarification of Terminology

The medical literature does not recognize "liver polyps" as a standard diagnostic category. Based on the available evidence, when clinicians encounter what appears to be a "liver polyp," they are typically observing one of the following:

Biliary Hamartomas (Von Meyenburg Complexes)

Biliary hamartomas are developmental malformations arising from ductal plate abnormalities during embryogenesis, not true polyps. 1

• These lesions represent part of the spectrum of ductal plate abnormalities that occur during fetal liver development 1
• They consist of dilated bile duct remnants embedded in fibrous stroma 1
• Biliary hamartomas have a prevalence of approximately 5.6% in the general population and are usually incidental findings 1
• They may occur in isolation or in association with other congenital conditions including Caroli disease, congenital hepatic fibrosis, and polycystic liver disease 1
• These lesions do not affect liver function and are often confused with miliary liver metastases on imaging 1

Portal Hypertensive Polyps (Gastric, Not Hepatic)

Portal hypertensive polyps occur in the stomach and gastrointestinal tract—not in the liver itself—as a consequence of portal hypertension from liver cirrhosis. 2, 3

• These polypoid lesions form in the gastric mucosa due to elevated angiogenesis associated with portal hypertension 3
• They are found in approximately 33.5% of patients with liver cirrhosis and portal hypertension 3
• Histologically, they show hyperplastic features with edema, vascular congestion, and smooth muscle hyperplasia 2
• All documented cases have been benign with no malignant transformation reported 3

Hepatocyte Polyploidy (Cellular Phenomenon, Not Polyps)

Hepatocyte polyploidy refers to cells containing multiple sets of chromosomes—this is a normal cellular adaptation in the liver, not a polyp formation. 4, 5

• Approximately 30% of human hepatocytes are polyploid, containing more than two sets of chromosomes 5
• Polyploidy develops during normal liver development, regeneration, and in response to various stresses 4
• This represents a cellular characteristic rather than a discrete lesion or mass 4, 5

Gallbladder Polyps (Adjacent Organ)

If the question refers to gallbladder polyps (which are adjacent to the liver), these form through distinct mechanisms:

Cholesterol polyps (60% of gallbladder polyps) form from cholesterol-laden macrophages accumulating in the gallbladder wall. 6

• These are nonneoplastic lesions with negligible malignancy risk 6
• They appear as small (<10mm), non-mobile, non-shadowing lesions on ultrasound 7, 6

Neoplastic gallbladder polyps arise from epithelial proliferation and dysplasia. 6

• Intracholecystic papillary neoplasms are mass-forming epithelial neoplasms ≥10mm 6
• These can progress through low-grade to high-grade dysplasia 6

Clinical Implications

When a patient presents with what appears to be a "liver polyp" on imaging, the clinician must determine the actual nature of the lesion:

• Biliary hamartomas: Require no intervention unless symptomatic; surveillance is not routinely recommended unless concurrent liver disease exists 1
• Cystic liver lesions: May require differentiation from biliary hamartomas using MRI characteristics 1
• Gallbladder polyps: Follow established size-based management algorithms (cholecystectomy for ≥10mm polyps, or ≥8mm in primary sclerosing cholangitis) 1, 6

The key pitfall is misidentifying the anatomic origin and nature of the lesion—precise imaging characterization is essential before determining management.