Gastric Polyps

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Basics

Mucosal lesions projecting above the gastric surface and into the lumen of the stomach

Description

  • Mostly benign with minimal malignant potential
  • Most commonly discovered as asymptomatic incidental findings on upper endoscopy (esophagogastroduodenoscopy [EGD])
  • Different types based on origin:
    • Epithelial (most common): fundic gland, hyperplastic, adenomas
    • Endocrine: carcinoid tumors
    • Infiltrative: xanthomas and lymphoid proliferations
    • Mesenchymal: gastrointestinal stromal tumor (GIST), leiomyoma, fibroma, lipoma
    • Inflammatory fibroid polyp

Epidemiology

Incidence
  • Incidence ~6% in the United States (1)
  • Male = female (1:1)
  • Frequency of polyp types:
    • Fundic gland: 13–77%
    • Hyperplastic: 18–70%
    • Adenoma: 0.5–3.75%
    • Carcinoid: <2%
    • Xanthoma: 0.3–3.9%
    • GIST: 1–3%
    • Inflammatory fibroid: 0.1–3%
    • Hamartomas: <1%
    • Others: <1%

Prevalence
Prevalence varies worldwide, estimated to be ~4% in United States. Fundic gland polyps (often arising in the setting of long-term proton pump inhibitor [PPI] use) are the dominant type. Polyps associated with Helicobacter pylori gastritis (hyperplastic and adenomatous) have become less common. Fundic gland polyps represent ~80% of polyps.

Geriatric Considerations
2/3 of gastric polyps are in patients >60 years old.

Pediatric Considerations
Gastric polyps are common in both children and adults with familial adenomatous polyposis (FAP) syndrome. Most often, these are fundic gland polyps.

Etiology and Pathophysiology

  • Fundic gland polyp
    • Sessile lesion usually <0.5 cm; found throughout the stomach
    • Most occur sporadically.
    • Associated with polyposis syndromes (FAP, MUTYH-associated polyposis [MAP], and gastric adenocarcinoma and proximal polyposis of the stomach [GAPPS])
    • Very low risk for malignancy (except in FAP syndrome)
    • Associated with long-term PPI use
    • Histology shows dilated oxyntic glands, lined by flattened parietal and mucous cells.
  • Hyperplastic polyp
    • Smooth, rounded (typically multiple) lesions, usually in the antrum
    • 0.5 to 1.5 cm—can be much larger
    • Hyperregenerative response of epithelium due to chronic inflammation (most commonly H. pylori)
    • Low risk for malignancy
      • Risk of malignancy in hyperplastic polyps increases with size (>1 cm) and pedunculation.
      • Loss of p16 and increased Ki-67 expression may indicate dysplasia in hyperplastic polyps.
  • Adenomatous polyp (raised intraepithelial neoplasia)
    • Typically associated with chronic atrophic gastritis
    • Velvety, lobulated, usually solitary lesion; most often found in the antrum; <2 cm
    • Considered to be premalignant
      • Malignant potential depends on size (>2 cm with 40–50% risk of malignant transformation) and degree of dysplasia and villous component.
  • Carcinoid polyp
    • Clusters of mucosal enterochromaffin cells; most often in the corpus or fundus
    • Derived from enterochromaffin-like (ECL) cells
    • Risk for metastasis depends on size.
    • Four distinct subtypes (type 1 most common)
  • Xanthoma
    • Small, yellow nodules or plaques that protrude from the surrounding pink gastric mucosa
    • Lipid-laden macrophages containing cholesterol and neutral fat embedded in the lamina propria
    • No malignant potential
  • GISTs
    • Neoplastic proliferations of interstitial cells of Cajal (or their precursors)
    • Well-circumscribed, submucosal lesions; most often in the fundus; median size 6 cm
    • Varying malignant potential based on size and mitotic activity
    • 50% of patients with GISTs >2 cm have metastatic disease at the time of presentation (usually liver).
  • Inflammatory fibroid polyp
    • Originates from submucosa; frequently with central depression or ulceration; 1 to 5 cm
    • No malignant potential
  • Hyperplastic and adenomatous polyps are associated with any inflammatory process causing chronic cell turnover.
  • Hamartomas
    • Abnormal growth of otherwise normal tissue
    • Benign; rarely invade or compress surrounding structures
  • All others: no known causes

Genetics
  • Most polyps have no known hereditary component.
  • Fundic gland polyps are associated with FAP arising from APC gene mutation.

Risk Factors

  • Increased incidence with age
  • Chronic gastritis: hyperplastic polyps
    • Chronic NSAID use, increased gastric secretions, erosions, or ulcers
  • Hypergastrinemia (gastrinoma, Zollinger-Ellison syndrome, long-term PPI use): fundic gland polyps
  • H. pylori: hyperplastic and adenomatous polyps
  • BRAF inhibitors used to treat melanoma may increase the risk for hypertrophic gastric polyps.

Commonly Associated Conditions

  • Associated with certain familial syndrome (1)[C]
    • Fundic gastric polyps: FAP
    • Hamartomas: Peutz-Jeghers syndrome, juvenile polyposis, Cronkhite-Canada syndrome, Cowden disease
  • Carcinoid polyps:
    • Type 1: achlorhydria, hypergastrinemia, and pernicious anemia
    • Type 2: Zollinger-Ellison syndrome, MEN1 syndrome

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