Are multiple polyps less than 1cm in size consistent with neoplastic or non-neoplastic pathology?

Multiple Polyps <1cm: Neoplastic or Non-Neoplastic Pathology?

Multiple polyps less than 1cm in size can be either neoplastic or non-neoplastic, and visual appearance alone is insufficient to reliably distinguish between them, making histological examination necessary for definitive diagnosis. 1, 2

Types of Small (<1cm) Polyps

Non-Neoplastic Polyps

• Hyperplastic polyps are the most common non-neoplastic lesions, typically small (<0.5 cm), sessile, and predominantly found in the rectosigmoid region 3
• Hyperplastic polyps constitute 18-70% of all gastric polyps and are usually single or few in number 4
• In a meta-analysis of 6280 diminutive polyps, approximately 45% were non-neoplastic 4

Neoplastic Polyps

• Adenomatous polyps (tubular, villotubular, or villous adenomas) are the most common neoplastic polyps 5
• Sessile serrated polyps (SSPs) are another type of neoplastic polyp that can be small in size 4
• Only 1-3% of conventional adenomas less than 5mm have advanced histologic features (high-grade dysplasia or villous histology) 4

Diagnostic Challenges

• Endoscopic diagnosis based on appearance alone has a sensitivity of 0.80 and specificity of 0.71 for adenomas, which is not accurate enough for clinical decision-making 2
• 22% of polyps described as hyperplastic by experienced endoscopists were actually adenomas, while 40% of those believed to be adenomas (1-5mm) were hyperplastic 1
• Even polyps less than 1cm in diameter can harbor invasive cancer, though this is rare 5

Clinical Significance and Management

Small Adenomatous Polyps

• Low-risk adenomas (<1cm) should have repeat colonoscopy in 10 years 4
• Multiple (3-10) small adenomatous polyps represent higher risk and warrant repeat colonoscopy in 3 years 4
• The NCI Pooling Project showed that with each additional adenoma, there is a linear increase in risk for both advanced and non-advanced neoplasia 4

Small Serrated Polyps

• Low-risk SSPs (<1cm with no dysplasia) should have repeat colonoscopy in 5 years 4
• SSPs ≥10mm or those with dysplasia are considered higher risk and should be offered surveillance colonoscopy at 3 years 4

Small Hyperplastic Polyps

• Distal hyperplastic polyps <1cm are generally considered to have minimal malignant potential 4
• The risk of advanced proximal neoplasia in persons with only hyperplastic polyps in the distal colon is comparable to the risk in persons with no distal polyps 4
• However, large (≥1cm) hyperplastic polyps may need to be managed more cautiously, similar to SSPs 4

Important Considerations

• Location matters: Hyperplastic polyps in the rectosigmoid are typically benign, while those in the proximal colon may have greater significance 4
• Number matters: Multiple polyps (>3) increase the risk of synchronous advanced neoplasia 4
• All polyps should be removed for histological examination as visual appearance cannot reliably distinguish between neoplastic and non-neoplastic pathology 1, 2
• Patients with multiple polyps (>20), especially at a young age (<40 years), should be evaluated for familial syndromes such as FAP 4

Common Pitfalls to Avoid

• Do not assume that small polyps are always hyperplastic and benign - invasive cancer can be found even in polyps less than 1cm 5
• Do not rely solely on endoscopic appearance to determine polyp histology - biopsy is necessary for accurate diagnosis 1, 2
• Do not ignore multiple small polyps - the presence of 3 or more adenomas of any size warrants closer surveillance 4
• Do not overlook the possibility of serrated lesions, which can be difficult to detect and have malignant potential 4