What is a rectal hyperplastic polyp and how should it be managed?

What is a Rectal Hyperplastic Polyp?

A rectal hyperplastic polyp is a benign, non-neoplastic growth in the rectum characterized by elongated crypts with a serrated "saw-tooth" appearance on histology, typically small (≤5 mm), pale in appearance, and carrying no increased risk of colorectal cancer when located distally. 1

Pathologic Features

Hyperplastic polyps are the most common non-neoplastic colonic lesions, representing approximately 45-50% of all diminutive polyps found at colonoscopy. 1 They consist of elongated crypts with characteristic serrated architecture, though they are not a homogeneous histologic category. 1

Key Histologic Variants

• Traditional hyperplastic polyps (THP): The most common subtype, typically small and distal, with no malignant potential 2
• Sessile serrated lesions (SSL): Atypical variants that are often large (≥1 cm), sessile, and proximally located with architectural abnormalities that can progress to microsatellite instability adenocarcinoma through the serrated pathway 1, 3
• Inverted hyperplastic polyps: Rare variants showing epithelial misplacement into the submucosa that can mimic adenocarcinoma but remain benign 4

Clinical Management Algorithm

For Small Distal Hyperplastic Polyps (<10 mm in Rectosigmoid)

Patients with small hyperplastic polyps in the rectosigmoid region should be rescreened as average-risk patients with colonoscopy in 10 years, as these carry no increased colorectal cancer risk. 3 This represents a strong recommendation with moderate quality evidence from the American Gastroenterological Association. 3

• Diminutive rectal hyperplastic polyps (≤5 mm) may be left in place if confidently identified using high-quality endoscopic imaging 1
• If resected, these do not require intensified surveillance beyond standard 10-year intervals 1, 3

For Large or Proximal Hyperplastic Polyps (≥10 mm or Proximal to Sigmoid)

Large (≥1 cm), sessile, proximally located hyperplastic polyps with atypical features must be completely removed and warrant surveillance similar to adenomas at 3-5 year intervals. 3 These lesions can harbor dysplasia or progress to cancer through the serrated adenoma pathway. 1

• Complete resection is essential, particularly for polyps showing irregular architecture or cytologic atypia 1, 3
• Follow-up colonoscopy should occur in 3-5 years (weak recommendation, very low quality evidence) 3
• Large solitary hyperplastic polyps in the right colon carry higher malignancy risk and require particular attention 3, 5

For Hyperplastic Polyposis Syndrome

Endoscopists must remain alert for hyperplastic polyposis syndrome, defined as: (1) ≥5 hyperplastic polyps proximal to the sigmoid with 2 being >1 cm, OR (2) any number of proximal hyperplastic polyps in a patient with a first-degree relative with the syndrome, OR (3) >30 hyperplastic polyps of any size throughout the colon. 1, 3

• These patients have markedly increased colorectal cancer risk (approximately 54% in one series) 3
• They require specialized management with frequent colonoscopic surveillance beyond standard intervals 3
• Optimal management protocols remain under study 1

Critical Diagnostic Pitfalls

Distinguishing Benign from High-Risk Lesions

The major challenge is that hyperplastic polyps are not histologically uniform. 1 Some variants (sessile serrated lesions) show atypical architectural and cytologic features that place them on a pathway to malignancy. 1

Key red flags requiring complete resection and closer surveillance include: 1, 3, 5

• Size ≥10 mm
• Proximal location (cecum, ascending colon, transverse colon)
• Sessile morphology
• Irregular surface pattern on magnified or enhanced imaging
• Central depression or ulceration

Rare Malignant Transformation

While traditional small distal hyperplastic polyps are benign, rare cases of adenocarcinoma arising in large hyperplastic polyps have been documented, particularly in the right colon. 5 One case series reported well-differentiated intramucosal adenocarcinoma in a 12-mm cecal hyperplastic polyp. 5 This underscores the importance of complete removal of larger lesions.

Mimics and Misdiagnosis

• Hyperplastic polyps with epithelial misplacement can simulate adenocarcinoma but remain benign 4
• Rare cases of duodenal-type follicular lymphoma can appear as hyperplastic polyps, though this is exceptionally uncommon 6
• Sessile serrated lesions may be misclassified as simple hyperplastic polyps, leading to inadequate surveillance 2

Quality Requirements for Surveillance Decisions

All surveillance recommendations assume: 3

• Complete examination to the cecum
• Adequate bowel preparation
• High confidence of complete polyp resection
• Adequate adenoma detection rate by the endoscopist

These recommendations do not apply to patients with hereditary colorectal cancer syndromes, inflammatory bowel disease, personal history of colorectal cancer, or strong family history of colorectal cancer, where shorter surveillance intervals are warranted. 3