Prevalence of subtypes of gastric intestinal metaplasia and its relationship with Helicobacter pylori infection

Materials and Methods: This was a cross sectional study done at Kathmandu Medical College teaching Hospital in Pathology department from December 2018 to August 2019. The endoscopic biopsies were evaluated for intestinal metaplasia and Helicobacter pylori with the help of Hematoxylin and Eosin stains as well as Giemsa stain. Subtypes of intestinal metaplasia were classified with the help of periodic acidSchiff/Alcian Blue stain combination and High Iron DiamineAlcian Blue stain at pH 2.5. The relationship between Helicobacter pylori and subtypes of intestinal metaplasia were compared. Fisher’s exact test was used for statistical evaluation. A p value of ˂ 0.05 was considered as statistically significant.


INTRODUCTION
Gastric intestinal metaplasia (IM) is a replacement of gastric mucosal epithelium by mucosal cells with intestinal morphology and is considered as a precursor lesion for gastric cancer. 1 Prevalence of gastric IM worldwide is unknown, however the study done by Sonnenberg and colleagues found 7% prevalence. 2 Based on the histomorphology and mucin-histochemistry, the gastric IM are classified as complete (type I) and incomplete (types II and III). It has been suggested that, chronic gastritis induced mainly by Helicobacter pylori (H. pylori) infection is usually associated with IM. 3 Several studies have shown the relation between gastric carcinoma and the subtype of IM, the incidence of cancer being highest among patients with IM subtype III. [4][5][6] The aim of the present study was to evaluate the prevalence of IM and its subtypes in gastric biopsy specimen. We also compared the relationship between H. pylori infection and subtypes of intestinal metaplasia. All the patients who meet the above criteria and undergoing upper gastrointestinal endoscopy during the study period were included. The biopsy was taken and fixed immediately in 10 % formalin solution. These were then processed in the tissue processor and embedded in paraffin wax. Serial sections were cut at 3-5µ. The biopsies were stained with hematoxylin and eosin (H&E) stain to evaluate for the presence of intestinal metaplasia. In addition Giemsa staining were carried out to determine for the presence or absence of H. pylori. These biopsies were then stained with periodic acid-Schiff/Alcian Blue (PAS/AB) at pH 2.5 stain combination and High Iron Diamine-Alcian Blue (HID/ AB) at pH 2.5 stain to identify neutral mucin, sialomucin and sulphomucin. These mucin stains (PAS/AB and HID/ AB) are not routinely used in histopathology for gastric biopsy samples. We used these stains to separate the types of IM. Additional cost was not charged to the patient for these stains. Subtypes of IM are determined according to Filipe et al classification. 7 Type I IM is characterized by the presence of mature absorptive and goblet cells, the latter secreting acid sialomucin. H. pylori was seen in 28(49.1%) biopsies. No statistical significant difference was found in the prevalence of types of gastric IM with H. pylori status (p˃0.05) ( Table 2).

DISCUSSION
The prevalence of gastric IM was found to be 12.2% in our study which is similar to the reported prevalence. 1,8 However in contrast to our study low prevalence of IM was observed in other studies, the possible cause for this might be less prevalence of H. pylori infection in their countries. 2,9 In a research of prevalence of gastric IM done in Turkey, the commonest IM found was type III (38%), followed by type II (32%) and type I (8.2%).1We also found type III as a commonest gastric IM. However in other studies done in Finland and Netherland higher prevalence of type I IM was reported. 6,10 This might be because we had higher prevalence of H. pylori infection and also the H. pylori eradication program was not active in our country.
It has been emphasized that sulphomucin secreting IM, that is type III is found significantly more often in surrounding dysplasia and gastric adenocarcinoma. 11 In our study we also found type III IM associated with dysplasia and adenocarcinoma in 4(7%) and 8(14.03%) cases respectively. DOI 10.3126/jpn.v10i1.28541

Figure 1: Intestinal metaplasia Type I: (A) PAS/AB stain, goblet cells secreting acid sialomucin. (B)HID-AB stain, absorptive cells mucin is predominantly neutral mucin (unstained) and goblet cells secreting sialomucin. (Magnification, X400)
The cause for this late diagnosis in our country is because patients were reluctant to do endoscopy and biopsy as per protocol for the early detection of precancerous lesions. Several studies suggested that routine endoscopic evaluation and histopathological follow up could be cost effective in patient with IM as this could detect gastric cancer at an early stage.

CONCLUSIONS
Gastric IM is a common finding in endoscopic biopsies. Type III subtype is more commonly observed than other subtypes. H. pylori can be absent in type III IM because of alteration in gastric environment. The practice of using PAS/AB and HID/AB stain is essential in routine histopathological examination to differentiate subtypes of IM.