How is atrophic gastritis classified according to distribution?

Classification of Atrophic Gastritis According to Distribution

Atrophic gastritis is classified into two main distribution patterns based on anatomic location: H. pylori-associated atrophic gastritis (HpAG), which begins in the antrum and progresses proximally, and autoimmune gastritis (AIG), which is corpus-predominant with antral sparing. 1

Primary Classification Systems

H. pylori-Associated Atrophic Gastritis (HpAG)

• Antrum-predominant pattern: Atrophic changes arise initially in the incisura and the antrocorporal transitional mucosa as small foci with loss of glands and intestinal metaplasia 1
• Progressive proximal spread: Over time, these foci coalesce to form larger patches of atrophic/metaplastic mucosa along the lesser curvature and antrum, eventually spreading to the corpus/fundus 1
• Multifocal distribution: This pattern is also termed "multifocal atrophic gastritis" or "environmental metaplastic atrophic gastritis" 2, 3

Autoimmune Gastritis (AIG)

• Corpus-predominant pattern: The typical histologic manifestation shows corpus and fundus involvement with destruction of individual oxyntic glands by lymphocytes 1
• Antral sparing: The antrum is characteristically spared in pure AIG 1, 3
• If antral atrophy is present in AIG: Concomitant H. pylori-associated atrophic gastritis should be considered 1

Risk Stratification Classification Systems

OLGA (Operative Link for Gastritis Assessment)

• Incorporates severity and topographic distribution of atrophic lesions as well-established determinants of gastric cancer risk 1
• Advocated by international guidelines for risk stratification of individuals diagnosed with precancerous gastric mucosal changes 1

OLGIM (Operative Link for Gastric Intestinal Metaplasia Assessment)

• Similar to OLGA but focuses specifically on intestinal metaplasia distribution and severity 1
• Both systems require separate specimen jars for corpus and antrum/incisura biopsies to accurately assess topographic distribution 1

Rare Variant: Atrophic Autoimmune Pangastritis

• Pangastric distribution: A distinctive form affecting both body and antrum diffusely, differing from classic variants 4
• Associated with systemic autoimmune disease: Characterized by intense mucosal inflammatory infiltrates persisting into severe atrophy phase 4
• Lacks neuroendocrine hyperplasia: Unlike typical AIG, and shows no association with H. pylori 4, 5

Clinical Implications of Distribution Patterns

• Extensive atrophy and metaplasia are associated with increased cancer risk regardless of distribution pattern 1
• Corpus-predominant atrophy leads to loss of gastric acidity and hypergastrinemia, with risk of type 1 gastric neuroendocrine tumors 1
• Proper biopsy technique is essential: Specimens from corpus and antrum/incisura must be placed in separate specimen jars following the updated Sydney protocol to accurately determine distribution 1

Common Pitfalls to Avoid

• Failing to obtain separate antral and corpus biopsies prevents accurate classification of distribution pattern 1
• Misidentifying pseudopyloric metaplasia as antral mucosa: Special stains (gastrin for antrum, pepsinogen I for corpus) can discriminate when anatomic location is uncertain 1
• Not recognizing that intestinal metaplasia presence almost invariably implies underlying atrophic gastritis, even when not explicitly noted on pathology reports 1