What is focal intestinal metaplasia?

Understanding Focal Intestinal Metaplasia

Focal intestinal metaplasia refers to the localized replacement of normal gastric epithelium with intestinal-type epithelium containing goblet cells, which is a precancerous condition that increases the risk of progression to gastric cancer. 1

Pathological Definition and Identification

• Intestinal metaplasia is characterized by the presence of goblet cells that stain intensely blue with Alcian blue (AB) due to acid mucins, distinguishing them from pseudogoblet cells (distended foveolar-type cells) that only stain with PAS but don't contain AB-positive acid mucins 1
• The term "focal" indicates that the intestinal metaplasia is present in limited or patchy areas rather than diffusely throughout the gastric mucosa 1
• Accurate recognition of intestinal metaplasia in biopsy samples is critical for establishing the correct diagnosis, as over-diagnosis is common (occurring in 38% of cases by general pathologists in community practice) 1

Clinical Significance and Risk Assessment

• Focal intestinal metaplasia is part of the Correa cascade of gastric carcinogenesis, representing an intermediate step between chronic gastritis and dysplasia/cancer 2
• The presence of intestinal metaplasia almost invariably implies the diagnosis of atrophic gastritis, which is associated with increased cancer risk 1
• The risk of progression to gastric cancer varies based on:
  • Extent of metaplasia (focal vs. extensive) 1, 2
  • Location (higher risk when present in the corpus) 1, 3
  • Presence of other risk factors such as H. pylori infection 4, 2

Diagnostic Approaches

• Standard endoscopy with biopsy is the most reliable means of establishing the diagnosis 1
• In most cases, intestinal metaplasia can be identified on standard H&E stained sections without special stains 1
• Special stains such as Alcian blue/PAS (AB/PAS) are not required routinely but can help confirm the diagnosis in select cases where:
  • Goblet cells are rare
  • Prominent "pseudogoblet cells" are present 1
• Image-enhanced endoscopy techniques (NBI, FICE, i-Scan) can improve visualization of areas with intestinal metaplasia 1

Differentiation from Other Types of Metaplasia

• Intestinal metaplasia must be distinguished from:
  • Gastric metaplasia (without intestinal features) 1
  • Pyloric gland metaplasia (also called pseudopyloric gland metaplasia), which indicates chronic mucosal inflammation 1
• Cytokeratin (CK) staining patterns can help distinguish intestinal metaplasia of the esophagus from intestinal metaplasia of the stomach 1
  • Barrett's esophagus shows superficial and deep CK7 immunoreactivity and superficial band-like CK20 staining 1

Management Implications

• H. pylori eradication is recommended when identified, as it reduces the risk of progression to dysplasia and cancer 4
• Surveillance strategies should be considered based on risk stratification:
  • Extensive intestinal metaplasia warrants closer surveillance than focal findings 4, 3
  • Risk assessment systems like OLGA (Operative Link for Gastritis Assessment) and OLGIM (Operative Link for Gastric Intestinal Metaplasia Assessment) can help guide management 1
• No universal surveillance guidelines exist, but American, British, and European gastroenterology societies suggest endoscopic surveillance in patients with risk factors for progression to gastric adenocarcinoma 4, 5

Common Pitfalls and Caveats

• Overdiagnosis of intestinal metaplasia is common when pseudogoblet cells are misinterpreted as true goblet cells 1
• The anatomic location of biopsies is crucial for proper interpretation; specimens from corpus and antrum/incisura should be placed in separate specimen jars 1
• Focal intestinal metaplasia can progress rapidly to gastric adenocarcinoma in some cases, highlighting the importance of appropriate follow-up 6
• The presence of focal intestinal metaplasia should prompt consideration of H. pylori testing if not already performed, as it is the most common etiologic agent worldwide 2, 3