Lesional patterns

 acute gastritis
 active gastritis (active focal gastritis)
 chronic gastritis

• lymphocytic gastritis
• collagenous gastritis
• granulomatous gastritis
• eosinophilic gastritis
• atrophic gastritis
• hypertrophic gastritis
• focally enhanced gastritis (#15371951#)

Etiology

 infectious gastritis

• CMV gastritis

 dysimmunity

• autoimmune gastritis
• Crohn gastritis
• gastric GVHD

 toxic gastritis
 radic gastritis
 foreign body (bezoard)
 periphery of a lesion

• gastric ulcer
• gastric carcinoma
• gastrectomy remnant
• digestive anastomosis ("stomitis")

 malnutrition
 hepatic cirrhosis
 endocrinian diseases

References

 Appelman HD. Gastritis: terminology, etiology, and clinicopathological correlations: another biased view. Hum Pathol. 1994 Oct;25(10):1006-19. PMID: #7927305#