Sacchi D, Guzzardo V, Guzzinati S, Pizzi M, Fassan M, Cesaro S, Pennelli G, Maddalo G, Albertoni L, Zanco F, Farinati F, Rugge M

8th Triennial Congress of Pathological Anatomy Siapec-iap 2019

Turin, 16-18 October  2019

Abstract

Introduction

 Autoimmune gastritis (AiG), an organ-specific disease restricted to oxyntic mucosa, is mediated by a complex interaction between autoantibodies (against parietal cell proton pump and/or intrinsic factor), and sensitized T-cells. The long-standing, non-self-limiting inflammation results into progressive destruction of the oxyntic glands, which are replaced by atrophic, non-metaplastic and metaplastic, mucosa (i.e. intestinal metaplasia [IM] and spasmolytic polypeptide-expressing metaplasia [SPEM]). Assessing histologically oxyntic atrophy (an essential step in gastritis staging) involves the distinction between the different atrophic phenotypes, which includes non-metaplastic (disappearance of glandular units replaced by a fibrotic lamina propria), and metaplastic (IM and/or SPEM) atrophy. SPEM is defined as antral-like (pseudo-pyloric metaplasia in hematoxylin-eosin [H&E]) mucosa, expressing immunohistochemical (IHC) markers natively associated to antral glands (trefoil factor 2 [TFF2]). Aims of this study were: i) to test the inter-observer consistency in the assessment of atrophy (i.e. non-metaplastic atrophy, IM and SPEM) in routine H&E histology; ii) to verify if/how TFF2-IHC modifies the histological assessment of SPEM, as obtained by H&E; iii) to explore if the SPEM-score, as obtained by applying TFF2-IHC, may result in any modification of the gastritis OLGA-stage as assessed by H&E.

Materials and methods

The study considered a series of 434 biopsy sets obtained from histologically-proved, serologically-confirmed AiG. Inclusion criteria were as follows: i) availability of a standard set of gastric biopsy samples (i.e. Sydney System compliant sets); ii) availability of immunohistochemical profiling, including TFF2 (Proteintech Group, Inc. IL, USA, 1:1500 dilutions; rabbit IgG). The study involved two pathologists working at the same Department (one GI expert [MR] and one in training [SAD]), where they shared the same diagnostic criteria and daily practice. To test the interobserver consistency (IOC) in the H&E assessment of the mucosa atrophy spectrum (non-metaplastic atrophy, IM atrophy, SPEM), 78/434 randomly selected biopsy sets (H&E stain) were considered by pathologists, who independently reported the atrophy scores. For each of the considered variables, the obtained score values were tested by k statistics.
All the original 434 histological sets (H&E and TFF2-IHC) were re-considered (SAD), by histologically scoring the whole spectrum of atrophy subtypes (OLGA staging tutorial1). In the biopsy samples obtained from the oxyntic mucosa, SPEM-atrophy was assessed by both H&E and TFF2-IHC; the consistency between the 2 score-values (H&E versus TFF2-IHC) was tested by k statistics.
Finally, to test if TFF2-IHC SPEM-scores could result in modifying: i) the “global” oxyntic score value, ii) and/or the conclusive OLGA-staging, this study compared the allocation of cases by stage when TFF2-IHC was applied additionally. The strength of association between OLGA stage and the pathological was obtained by applying Student’s t-test and the Wilcoxon non-parametric test for matched pairs, as appropriate. The statistical analysis was performed using the STATA 8.0 software (Stata Corporation, College Station, TX, USA).

Results

Among the 78/434 biopsy sets reviewed by two pathologists, the IOC was tested by means of k statistics. IOC was ranked as ‘good’ in corpus IM (no change=84,6%; k coefficient = 0,7656), as well as, in antral IM (no change=93,6%; k coefficient= 0,620), and as ‘excellent’ in SPEM (no change=88,5%; k coefficient=0,8295). The IOC was ranked as ‘weak’ in non-metaplastic atrophy (no change=28,2%; higher score=71,8%; k coefficient=0,0314; the discrepancy range: 5% to 15%). ‘Excellent’ inter-observer consistency was documented in the assessment in the score of both “global” oxyntic (no change =100%; k coefficient =1), and “global” antral atrophy score (no changes=98,7%; k coefficient =0,926) and, ultimately, in OLGA stage assessment (no change=98,7%; k coefficient = 0,9536). When all the 434 cases were considered, no differences emerged by comparing the SPEM-atrophy scores as obtained from H&E versus TFF2-IHC assessments, (‘excellent’ k statistics; no change=85,7%; higher score at TFF2-IHC=7,4%, and lower score at TFF2-IHC=6,9%; k coefficient= 0,8365). Furthermore, no differences emerged in corpus atrophy scores (no change=94,0%; higher score at TFF2-IHC=3,9%, and lower score at TFF2-IHC=2,1%; k coefficient= 0,8997). Finally, “excellent” consistency emerged in the allocation of cases by OLGA-stage: no change in 95,2%; higher stage at TFF2-IHC in 2,9%, and lower stage at TFF2-IHC in1,8%; k coefficient= 0,889.

Conclusions

In AiG, the present results demonstrate that the TFF2 stain does not significantly improve the histological assessment of SPEM. TFF2-IHC, however, may help pathologists who are not familiar with gastritis atrophy-assessment. In such a diagnostic setting, OLGA-staging of AiG is not significantly modified by the additional information achievable by including TFF2-IHC to the routine histological stain.