Helicobacter pylori Gastritis: Atypical Infections May Be Missed Without the Regular Use of Special Stains

Abstract

Introduction: In most patients, Helicobacter pylori infection causes chronic active gastritis, a pattern that prompts pathologists to search for organisms including the use of special or immunohistochemical (IHC) stain. In some cases, the infection may be difficult to detect because organisms are rare, morphologically altered, confined to unusual locations, or devoid of the characteristic chronic active inflammation, making the infection deceptively unsuspected. Without the aid of special staining techniques, such cases could be missed even by a diligent pathologist. This study was designed to determine the prevalence of these atypical infections. Methods: All gastric biopsies received at a single anatomic pathology laboratory over a 6-month period were stained for H. pylori by IHC (90%) or with the use of HP blue or Alcian yellow special stains (10%). All biopsies with H. pylori were classified by the sign-out pathologist as either “typical” (THP) or “atypical” (AHP) infection. The criterion for a “typical” infection was the presence of chronic active gastritis with abundant organisms. “Atypical” infections were those in which H. pylori was 1.) unexpected because of the lack of suggestive histologic findings, or 2.) difficult to detect, either because of an unusual location within the gastric mucosa or very small numbers of organisms. Results: Gastric biopsies were received from a total of 80,218 patients during the study period. Of the 7,510 H. pylori-positive biopsies classified either as AHP or THP, 938 (12.5 %) were considered atypical. The most common type of atypical infection was rare H. pylori organisms (<10 organisms per section) (72.9%), followed by unusual mucosal histology (minimal or no inflammation, 8.8%), organisms only in the deeper portions of oxyntic glands (8.4%), and organisms found in the body but not antrum (9.1%). Conclusion: In this series, H. pylori infection was not readily detectable in a significant proportion of our biopsy specimens. While in some cases careful scrutiny might have eventually prompted the pathologist to examine a special stain, cases with essentially no inflammation and those in which organisms were relegated into the depth of oxyntic glands could not have been reasonably suspected and would have been missed. The performance of a sensitive special stain adds only a small percentage to the total cost of an EGD; yet it could save a sizable segment of infected patients: 1.) additional tests and repeat endoscopy, 2.) the risk of developing peptic ulcer and gastric cancer, and 3.) acting as a potential source of infection for family members. Disclosure - All authors are employees of Miraca Life Sciences, Irving, Texas.