Secondary Prevention of Epidemic Gastric Cancer in the Model of Helicobacter pylori -Associated Gastritis

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1 H. pylori Infection, Gastric Cancer and Related Pathologies Secondary Prevention of Epidemic Gastric Cancer in the Model of Helicobacter pylori -Associated Gastritis Marco Pizzi a Deborah Saraggi a Matteo Fassan b Francis Megraud d Francesco Di Mario c Massimo Rugge a a General Pathology and Cytopathology Unit, Department of Medicine-DIMED, University of Padova, Padova, b ARC-NET Research Centre, University of Verona, Verona, and c Gastroenterology Unit, Department of Medicine, University of Parma, Parma, Italy; d Centre National de Référence des Hélicobacters et Campylobacters, Bordeaux, University of Bordeaux, Bordeaux, France Key Words Helicobacter pylori Atrophic gastritis Gastric cancer OLGA staging system Abstract Irrespective of its etiology, long-standing, non-self-limiting gastric inflammation (mostly in Helicobacter pylori -associated cases) is the cancerization ground on which epidemic (intestinal-type) gastric carcinoma (GC) can develop. The natural history of invasive gastric adenocarcinoma encompasses gastritis, atrophic mucosal changes, and intraepithelial neoplasia (IEN). The topography, the extent and the severity of the atrophic changes significantly correlate with the risk of developing both IEN and GC. In recent years, both noninvasive (serological) tests and invasive (endoscopy/biopsy) procedures have been proposed to stratify patients according to different classes of GC risk. As a consequence, different patient-tailored GC secondary prevention strategies have been put forward. This review summarizes the histological features of H. pylori -related gastritis and the natural history of the disease. Histological and serological strategies to assess GC risk as well as the clinical management of atrophic gastritis patients are also discussed S. Karger AG, Basel Introduction Helicobacter pylori -related gastritis is one of the leading precancerous conditions for nonhereditary gastric adenocarcinoma. H. pylori infects approximately 50% of the world s population, with even higher prevalence in several developing countries [1, 2]. The bacterial colonization consistently results in gastric mucosa inflammation (i.e. gastritis). Due to a complex interplay of both host-related and environmental situations, a subset of the infected patients progresses to more severe organic and functional changes of gastric mucosa, basically consisting in phenotypic modifications of the native population of gastric glands (mucosa atrophy) [3]. Gastric mucosa atrophy is the cancerization ground on which neoplastic gastric transformation (both intraepithelial neoplasia, IEN, and invasive gastric carcinoma, GC) eventually develops [4]. A comprehensive understanding of both the clinical and the biological features of H. pylori -related gastritis is of paramount importance in any consistent assessment of the gastritisassociated GC risk; such a risk stratification is necessarily required in establishing any strategy aimed at secondary prevention of GC [5]. karger@karger.com S. Karger AG, Basel /14/ $39.50/0 Massimo Rugge Surgical Pathology and Cytopathology Unit Department of Medicine-DIMED, University of Padova Via Aristide Gabelli 61, IT Padova (PD) (Italy) unipd.it

2 a c Fig. 1. Histological features of native gastric mucosa. a In the gastric antrum, the foveolae occupy one third of the whole mucosal thickness. Both the foveolar and the glandular structures are covered by tall mucus-secreting epithelial cells. b Scattered gastrinproducing G cells are located in the upper portion of the gastric glands. c The oxyntic mucosa is characterized by short foveolar tips and densely packed straight glandular tubules. Glandular structures are mainly composed of principal and parietal cells (insert) that occupy the lower and mid-part of the gland, respectively. Gastric stem cells are located just beneath the foveolar tips. d In the oxyntic mucosa, neuroendocrine enterochromaffin-like cells are located at the glands base. HE and immunoperoxidase stain. Original magnification 20. This review addresses the phenotypic changes occurring in H. pylori -related gastritis and the natural history of the disease. The stratification of patients according to GC classes of risk and their clinical management will also be addressed. The Anatomic and Functional Context Any approach to the description/understanding of gastric inflammatory diseases largely relies on some basic notions concerning the anatomy of gastric mucosa. The surface (luminal) epithelium of gastric mucosa proceeds in the glandular structures, which are embedded in a supporting stromal tissue (lamina propria), surrounding each glandular unit. The muscularis mucosae b d (a thin smooth muscle layer) lies immediately below the lamina propria, forming a continuous rim separating the mucosa from the connective tissue of the submucosa. The luminal surface of the gastric mucosa is covered by columnar epithelia, which also line the tubular folds of the surface epithelium (gastric foveolae). The foveolae continue into the glandular structures. Both surface and glandular epithelial cells rest on a basal membrane, separating the epithelia from the nonepithelial (stromal) mucosa compartment. Glandular structures are embedded within (structurally supported by) a fine meshwork of reticulin and collagen fibers. This supporting tissue (lamina propria) also includes loosely arranged fibroblasts and vascular blood/lymphatic channels. Rare smooth muscle fibers may extend upward from the muscularis mucosae into the lamina propria. A scattered population of leucocytes (histiocytes, lymphocytes, plasma cells, rare polymorphs and mast cells) is dispersed within the stromal interglandular tissue. According to both the phenotype and function of gastric glands, the stomach consists of two distinct anatomical and functional compartments: (a) the distal antropyloric, and (b) the cranial corpus-fundic regions ( fig. 1 ). In both the most proximal and most distal parts of gastric mucosa, however, two additional areas have also been histologically characterized (so-called cardial and juxtapyloric mucosa, respectively). In gastric inflammatory diseases, however, the involvement of these last two regions is basically consistent with that of their adjacent mucosa, which excludes any more detailed description. The transition between antral (mucus-secreting) and corpus (oxyntic) mucosa is not abrupt, and the intervening junctional mucosa is characterized by a mixed glands phenotype [6, 7]. In the antral region, the foveolae occupy approximately one third of the whole mucosal thickness. Both superficial and foveolar columnar epithelia consist of tall mucus-secreting cells, with basally located nuclei. The coiled structures of the antral mucus-secreting glands are embedded within an abundant lamina propria. Glandular coils consist of pale (PAS-positive) epithelia, which produce neutral mucins and bicarbonate [8]. Neuroendocrine gastrin-secreting cells (G cells) are dispersed among the mucin-producing cells. G cells are mainly located in the gland neck, just below the gastric foveolae ( fig. 1 a, b) [9]. The oxyntic mucosa is characterized by short foveolar tips (less than one quarter of the mucosal thickness) opened into densely packed, straight glandular tubules. Glandular epithelia consist of three distinct cell types, oc- 266 Pizzi /Saraggi /Fassan /Megraud /Di Mario / Rugge

3 cupying different parts of the glands. Just beneath the foveolar tips, the gland isthmus is populated by stem cells which can differentiate into either surface mucus-secreting columnar or deeper specialized oxyntic epithelia [10, 11]. The mid-part of the gland (i.e. the neck) includes chloride acid- and intrinsic factor-secreting parietal cells [6, 7]. Parietal cells display striking ultrastructural features: their apical membrane consists of crescent-shaped microvillous canaliculi, and their cytoplasm is occupied by hundreds of mitochondria [12, 13]. The most distal part of the corpus glands (i.e. the base) harbors neuroendocrine cells (i.e. enterochromaffin-like cells) and pepsinogen I (PgI)-producing chief cells ( fig. 1 c, d) [6, 7]. Gastric glands synthesize and secrete two biochemically and immunologically different types of Pg, the nonactivated precursor of the digestive enzyme pepsin: (a) PgI (also referred to as pepsinogen A), and (b) PgII (or pepsinogen C). While PgI is exclusively secreted by corpus parietal cells, PgII is produced by both the fundic and antral mucosa [14 16]. In the normal stomach, the corpus-fundic compartment is more widespread than the antral one. As a result, the production of PgI (marker of oxyntic mucosa) largely exceeds that of PgII, and the ratio of serum PgI to PgII is about 4: 1 [14 16]. Gastritis Definition and Etiology Gastritis is defined as (histologically confirmed) inflammation of the gastric mucosa [17]. Gastric inflammation may result from both transmissible and nontransmissible etiological agents. At the clinical level, gastritis is usually classified as acute and chronic; such a distinction, however, is not supported by any discriminating profile of the inflammatory infiltrate. Consistent with both their etiology and their clinical outcome, gastric inflammatory diseases can be clinically distinguished between self-limiting and non-self-limiting, only the latter being involved in long-term organic and functional alterations of gastric mucosa. Table 1 lists the most common etiological variants of gastric inflammatory diseases. Histology Profile and Gastritis Natural History The Inflammatory Trait By definition, the inflammatory infiltrate within the lamina propria (i.e. mononuclear cells and polymorphs) is the necessary pathological trait of gastric inflammatory diseases. The amount of the mononuclear infiltrate (i.e. Table 1. Etiological variants of gastric inflammatory conditions Etiologic category Transmissible agents Chemicals Physical agents Immune-mediated Idiopathic Agents GvHD = Graft-versus-host disease. Virus Bacteria Fungi Parasites Dietary agents Drugs Bile (biliary reflux) Radiation Autoimmune Drugs Food-mediated GvHD Crohn s disease Sarcoidosis Vasculitis lymphocytes, plasma cells and histiocytes) defines the gastritis intensity; visual analogue scales have been provided as a useful guide to histologically score the amount of the mononuclear infiltrate ( fig. 2 a c). In gastritis of low and moderate intensity, lymphocytes and plasma cells expand the lamina propria, surrounding gastric glands without affecting the overall mucosal architecture; nodular lymphoid aggregates are rarely seen ( fig. 2 a, b). Structured lymphoid follicles can only be observed in high-intensity gastritis, whose inflammatory infiltrate can even obscure gastric glandular architecture ( fig. 2 c). Such a situation may affect the quantitative histology assessment of gastric units (in such cases a histology categorization of indefinite for atrophy has been suggested) [17, 18]. Lymphocytes replacing (or partially destroying) glandular structures (i.e. lymphoepithelial lesions) are highly suggestive of mucosa-associated lymphoid tissue lymphoma (MALT lymphoma, whose pathogenesis is strictly related to H. pylori infection) [19]. Lymphoepithelial lesions should be distinguished from (more bland) intraglandular lymphocytic infiltrate, which is considered the hallmark of lymphocytic gastritis (a peculiar form of gastritis, suggestive of immune-mediated etiology) [20]. Polymorph granulocytes (infiltrating either the lamina propria and/or the glandular lumen) are the well-established markers of the gastritis activity [18]. H. pylori-related Gastritis 267

4 Fig. 2. Intensity and activity of gastric inflammatory infiltrates. a c Lymphocytes, plasma cells and monocytes define the intensity of the ongoing inflammatory process. a In low-intensity gastritis, a scanty inflammatory infiltrate is dispersed within the lamina propria. b In moderate-intensity gastritis, the lymphomonocytic infiltrate is more florid without evidence of nodular aggregates that only characterize high-intensity cases ( c ). d f Gastritis activity is defined by the presence and the location of polymorph granulocytes. d Mild activity is characterized by granulocytes infiltrating only the lamina propria. e Moderate activity features polymorphs infiltrating the gastric glandular structures. f Severe activity is characterized by intraglandular micro-abscesses (i.e. polymorphs within glandular lumens). HE stain. Original magnification 20 and 40. metaplastic changes of the native gastric glands) result in a loss of the native gland population: the current definition of atrophy as loss of native glands includes both of these conditions ( fig. 3 ). In H. pylori -associated gastritis, atrophic changes are featured earlier at the level of the angular (transitional) mucosa (also known as atrophic border [21] ), later involving the mucus-secreting antral compartment (i.e. antral-restricted atrophic gastritis). The topographical spreading of the atrophic changes is basically consistent with the topography of the earlier inflammatory lesions. As for the antrum to corpus spreading of the inflammatory lesions, also the H. pylori -associated atrophic changes extend proximally from the antrum to the oxyntic mucosa, giving rise to the clinicopathological picture of atrophic multifocal or diffuse atrophic pan-gastritis [22]. Because the corpus-spreading inflammation announces H. pylori -dependent oxyntic atrophy, some authors attribute to the nonatrophic corpus gastritis an increased risk of GC (in comparison with the simple antrum-restricted gastritis) [23]. In the model of pure (non- H. pylori-associated) autoimmune gastric inflammation, the antrum is virtually unaffected by inflammatory lesions, which basically result from the autoimmune aggression targeted against the parietal cells. As previously described for the H. pylori model, also in this pathological condition, the earlier phase of the (corpus-restricted, immune-mediated) inflammation may progress to atrophic changes (corpusa b c d e f The gastritis activity can be semiquantitatively scored as mild (granulocytic infiltrate limited to the lamina propria), moderate (granulocytes localized among glandular cells) or severe (intraglandular micro-abscesses; fig. 2 d f). To achieve more consistent interobserver agreement, a two-level scale (low-grade vs. high-grade activity) would be advisable. In H. pylori -associated gastritis, the semiquantitative assessment of H. pylori has been advised. Such a histology score has been demonstrated with no or negligible clinical impact. Successful H. pylori eradication results in the disappearance of the polymorph infiltrate. The persistence of granulocytes is thus indicative of an ongoing H. pylori infection (unsuccessful eradication) [18]. Mucosa Atrophy: Natural History Long-standing inflammation (due to both transmissible and nontransmissible agents) may result in phenotypic (and functional) changes of the epithelial compartment. Irrespective of its etiology, long-standing, non-selflimiting inflammation causes structural damage to the glands units (both oxyntic and mucus-secreting), eventually resulting in glandular loss (lamina propria desertification). Alternatively, several inflammation-related molecular deregulations may interfere with the mechanisms modulating the original commitment of the gastric epithelia, resulting in newly appearing phenotypes of the epithelial cells (i.e. gastric epithelial metaplasia). Both of these conditions (gastric mucosa desertification and 268 Pizzi /Saraggi /Fassan /Megraud /Di Mario / Rugge

5 Fig. 3. Histological phenotypes of (atrophic and nonatrophic) gastritis. a Nonatrophic gastritis is characterized by a mixed inflammatory infiltrate within the lamina propria without any loss of appropriate glands. b In metaplastic atrophy, native gastric glands are replaced by fully differentiated glandular structures that are inappropriate for the anatomic location (IM, shown in b, and/or pseudo-pyloric metaplasia). c Nonmetaplastic atrophy is characterized by reduction/shrinkage of native gastric glands that are replaced by a thickened and fibrotic lamina propria. HE. Original magnification 4. a b c restricted atrophic gastritis of autoimmune type). Some evidence is available demonstrating that the immunemediated corpus disease could be also related to a longstanding H. pylori infection, able to trigger an autoimmune aggression against structural antigens expressed by parietal cells. This secondary immune-mediated corpus gastritis does not exclude primary gastric autoimmunity, as supported by the consistent demonstration of antiparietal cell autoantibodies, frequently detectable in association with several primary (extragastric) autoimmune diseases. a b Mucosa Atrophy: Histology Phenotypes Gastric mucosa atrophy is defined as loss of native/ appropriate glands [17, 18, 24]. This definition is based on the functional and histological heterogeneity of normal gastric mucosa [24 26]. Gastric mucosa atrophy includes two main histological variants: (a) nonmetaplastic, and (b) metaplastic ( fig. 3 b, c; fig. 4 ) [24]. Nonmetaplastic atrophy is defined as (partial or complete) disappearance/shrinking of native gastric glands, with fibrotic expansion (i.e. micro-scarring) of the lamina propria. Unlike metaplastic atrophy, the reduced number of appropriate glands (antrum: mucus-secreting; corpus: oxyntic) is not accompanied by any change in their original phenotype ( fig. 3 c; fig. 4 a). Nonmetaplastic atrophy should be histologically distinguished from those expansions of the lamina propria due to muscularis mucosae hyperplasia, as occurring in chemi- c Fig. 4. Histological features of gastric mucosa atrophy. a In nonmetaplastic atrophy, native gastric glands are reduced and substituted by a fibrotic lamina propria. b In IM, the native glandular structures are replaced by well-differentiated intestinal-type epithelia. c Occasionally, both nonmetaplastic and metaplastic (IM) atrophy can be seen. d In pseudo-pyloric metaplasia, the original commitment of oxyntic mucosa can be demonstrated by immunostaining for PgI. HE and immunoperoxidase stain. Original magnification 10. d H. pylori-related Gastritis 269

6 a c Fig. 5. Different phenotypes of IM. a On histology, IM is defined by the presence of mucin-secreting goblet cells (top right), Paneth cells (lower left) or both. b d According to Felipe and colleagues, IM can be classified based on the different mucin expression profiles. b Type I IM is characterized by goblet cells secreting sialomucins only. c Type II IM features the expression of both sialomucins and sulfomucins. d Type III IM is characterized by goblet and/or columnar cells secreting sulfomucins only. HE, Alcian blue and high-iron diamine stains. Original magnification 40. b d cal/reactive gastropathy, or prolonged proton pump inhibitor administration [17, 27]. The metaplastic variant of gastric atrophy consists in the replacement of native glands by glandular structures featuring a new (anatomically inappropriate) epithelial commitment. While the actual number of glandular units is not necessarily reduced, their phenotype is out of place for the anatomic location. A huge amount of epidemiological, clinical and biological studies support the increased neoplastic risk associated with metaplastic transformation: overall, the most basic observation is the strict similarity between intestinalized gastric mucosa and intestinal-type GC. Two main types of inappropriate differentiation (metaplasia) can be found: (a) pseudo-pyloric metaplasia, and/or (b) intestinal metaplasia (IM; fig. 4 b d). By definition, pseudo-pyloric metaplasia (also known as spasmolytic polypeptide-expressing metaplasia) may only affect oxyntic glands (corpus-fundic mucosa). Native oxyntic glands are replaced by antral-like glandular units, lined by mucus-secreting epithelia. The original oxyntic commitment of the metaplastic cells can be demonstrated by their chimerical (scattered) immunohistochemical expression of PgI ( fig. 4 d) [28, 29]. IM can affect both natively (mucus-secreting) antral and metaplastic (pseudo-antralized) oxyntic epithelia. The histological diagnosis of IM is based on the detection of mucin-producing goblet cells, and/or Paneth cells (fig. 4b, c; fig. 5a) [30]. Based on hematoxylin-eosin (HE) histology, histochemistry and immunohistochemistry, several classifications of gastric IM have been proposed [8, 31 33]. All of them aim at establishing a prognostic link between specific IM variants and elective risk of IM to GC progression. On HE stain, metaplastic columnar and goblet epithelia can be easily distinguished into two phenotypes: the first, more similar to small-bowel mucosa (columnar epithelia featuring brush border, and presence of Paneth cells: small intestinal type, or complete-type IM); the second recalling the cell population of the colonic crypts (absence of brush border, more irregular luminal membrane, absence of Paneth cells: colonic type, or incomplete-type IM) [31]. Matsukura et al. [31] distinguish IM according to the presence/absence of small intestinal enzymes (i.e. sucrose α- D -glucohydrolase, α-trehalase, microsomal aminopeptidase and alkaline phosphatase): (a) the complete-type IM is associated with the full (or nearly full) expression of such enzymes; (b) the incomplete-type IM is characterized by their complete (or almost complete) absence. Sophisticated histochemical techniques subcategorize IM according to its acid mucin secretion, as assessed by high-iron diamine stain (sialomucins: blue stain vs. sulfomucins: brown stain). While such a classification is highly specific in discriminating the mucin secretion, its routine application is significantly limited by two major weaknesses: (a) the chemical reagents involved into the histochemical reaction are potentially toxic, and (b) the mucin pattern assessment is highly subjective due to the frequent occurrence of different mucin patterns in the same single case. According to the acid-mucin expression profiles, Filipe and colleagues distinguish 3 IM variants: (a) type I (with goblet cells secreting sialomucins only); (b) type II (with goblet cells secreting both sialomucins and sulfomucins); (c) type III (with goblet and columnar cells secreting sulfomucins only; fig. 5 b d). Filipe s type I basically corresponds to complete IM, while types II and III are both included among the Matsukura s incomplete (colonic-type) IM [8, 33 34]. 270 Pizzi /Saraggi /Fassan /Megraud /Di Mario / Rugge

7 The biological relationship between Filipe s types of IM is still debated [35 37]. Because different mucin patterns can be faced within the same metaplastic epithelium, it has been suggested that the IM subtypes represent a biological continuum of the same pathophysiological process: in early IM, (native) gastric neutral mucins are replaced by acid sialomucins. As the metaplastic phenotype progresses, sulfomucins become dominant and they more closely predict a neoplastic transformation [30]. As such, sulfomucins represent a highly sensitive and specific marker of long-standing metaplastic atrophy, and their presence has been associated with the highest risk of developing GC [8]. Several studies consistently support the assumption that mucin profiling not only correlates with the age of the metaplastic transformation, but also significantly correlates with the extent/topography of the gastric intestinalization. This well-established observation significantly lowers the clinical impact of the IM subtyping, also conferring a primary importance to the endoscopy/histology assessment of IM spreading within gastric mucosa. Atrophic Gastritis and Gastric Carcinogenesis Intestinal-type (epidemic) GC is triggered by longstanding inflammatory conditions, which, in turn, result in a well-established pattern of phenotypic changes [38]. This sequence of phenotypic and molecular changes is currently known as Correa s multi-stage cascade of gastric carcinogenesis [3]. In the Correa s carcinogenic cascade, the initial step is represented by the inflammatory lesions and their associated atrophic progression; the latter is the cancerization ground on which advanced precancerous lesions (APLs) and GC finally develop. APLs are considered as phenotypic alterations bridging the gap between atrophic/metaplastic changes and overt invasive carcinoma [3]. Originally defined in the Western literature as epithelial dysplasia [39, 40], APLs are currently referred to as IEN [41]. The diagnosis of gastric IEN is based on the combination of three morphological abnormalities: (a) cytological atypia; (b) loss of the native epithelial commitment, and (c) disruption of mucosal architecture. The severity of these phenotypic changes defines two grades of IEN, i.e. low-grade (LG-IEN) and high-grade IEN [42]. The phenotypic and molecular distinction between atypical gastric hyperplasia and LG-IEN can be occasionally challenging. To overcome such diagnostic problems, a provisional label of indefinite for IEN has been proposed by two international APL classifications (i.e. the Padova International [42] and Vienna Classification [43] ). Two variants of indefinite for IEN lesions have been described: atypical foveolar hyperproliferation (afh) and hyperproliferative IM (HIM). afh is usually found in native (i.e. nonmetaplastic) glands undergoing reactive inflammatory modifications; HIM consists of foci of closely packed metaplastic glands, with variable cytological atypia [42]. The long-term follow-up of lesions indefinite for IEN reveals that cases defined as afh never progress to true-ien, whereas a small percentage of hyper-him is associated with subsequent progression to LG-IEN (6% of cases) [44]. The Gastritis Staging Systems Several studies consistently demonstrate that the risk of (intestinal-type) GC significantly correlates with the extent of gastric mucosa atrophy [22, 45, 46]. Building on such observations, an international group of gastroenterologists and pathologists (the Operative Link for Gastritis Assessment, OLGA) has proposed a system for reporting gastric atrophy in terms of stage (the OLGA staging system) [17, 47, 48]. The OLGA stage is obtained by combining the extent of atrophic changes (histological evaluation) with their topographical location (as obtained by a well-established protocol of biopsy sapling of antral and corpus mucosa [49] ). A reliable OLGA stage is thus only assessable in the presence of a representative gastric mucosa biopsy sampling. In line with the updated Sydney System biopsy protocol [49], the OLGA Staging System recommends that at least 5 biopsy samples be taken from (a) the greater and lesser curvatures of the distal antrum (2 biopsy cores); (b) the lesser curvature at the incisura angularis (1 biopsy core), and (c) the anterior and posterior walls of the proximal corpus (2 biopsy cores). Additional biopsy samples should be obtained for any focal lesion documented at endoscopy. For each biopsy core, atrophy is assessed as the overall percentage of (metaplastic and nonmetaplastic) atrophic mucosa. The extent of atrophy is scored on a four-tiered scale (score 0: no atrophic glands; score 1: 1 30% of atrophic glands; score 2: 31 60% of atrophic glands; score 3: >60% of atrophic glands). Using this scale, an overall atrophy score is assigned to each gastric anatomic compartment (i.e. the antral and the oxyntic mucosa). The OLGA H. pylori-related Gastritis 271

8 Fig. 6. The OLGA Staging System for gastric mucosa atrophy. The extent of gastric mucosa atrophy is first assessed for each gastric anatomic compartment (i.e. the antropyloric and the corpus-fundic region). The overall OLGA stage is then obtained by matching the antral with the oxyntic atrophy score. ATROPHY SCORE Score 0: no atrophic glands Score 1: 1 30% of atrophic glands Score 2: 31 60% of atrophic glands Score 3: >60% of atrophic glands ANTRUM No atrophy (score 0) (including incisura angularis) Mild atrophy (score 1) (including incisura angularis) Moderate atrophy (score 2) (including incisura angularis) Severe atrophy (score 3) (including incisura angularis) No atrophy (score 0) CORPUS Mild atrophy (score 1) Moderate atrophy (score 2) STAGE 0 STAGE I STAGE II STAGE II STAGE I STAGE II STAGE I STAGE II STAGE II STAGE III Severe atrophy (score 3) STAGE III STAGE IV STAGE III STAGE III STAGE IV STAGE IV stage is then obtained by matching the antral with the oxyntic atrophy score ( fig. 6 ) [50]. The OLGA system ranks gastritis on a scale of increasing disease severity (from OLGA stage 0 to OLGA stage IV) [50]. Many studies conducted on European, Asian, and South-American populations have demonstrated that patients with high-risk OLGA stages (i.e. OLGA stage III and IV) are at increased risk of both APLs and GC [51 53]. Furthermore, high-risk OLGA stages have also been associated with extensive (cancer-prone) sulfomucin type IM, which further supports their unfavorable prognostic meaning [54]. More recently, by embracing the gastritis staging philosophy, some authors proposed a gastritis staging system based on the sole assessment of IM (the Operative Link on Gastric Intestinal Metaplasia, OLGIM) [55]. Despite its interobserver reproducibility, the OLGIM proposal is significantly less sensitive than the OLGA system in detecting high-risk patients [56]. This reduced sensitivity is mainly attributable to the downstaging of some atrophic nonintestinalized cases (i.e. spasmolytic polypeptide-expressing metaplasia glands) which are actually part of the cancerization process. As recently reported by the Maastricht IV statements, the OLGA staging system provides extremely useful information regarding the extent and severity of atrophic gastritis and contributes to the planning of secondary prevention strategies tailored to each patient s GC risk: high OLGA stage patients (stage III and IV) should undergo endoscopy-biopsy follow-up, whereas low OLGA stages (stage 0, I and II) can be only clinically or serologically monitored [5]. Serological Markers for Gastric Mucosa Atrophy Both the invasiveness and high costs of endoscopy-biopsy procedures limit their widespread use as GC secondary prevention strategies. To overcome such limitations, serological tests have been recently proposed aimed to stratify gastritis patients according to the severity of the gastric mucosa atrophy and, ultimately, according to their atrophy-associated GC risk [5, 57]. These new approaches are largely based on the assessment of the functional status of gastric mucosa as established by serologically testing two main pro-enzymes produced by gastric mucosa: PgI, PgII, and their ratio (PgI/PgII). In particular, serum levels and ratio are linked to the functional status of corpus-fundic glands [58, 59]. Any decrease in oxyntic chief cells (i.e. corpus mucosa atrophy) is indeed paralleled by a reduction of both PgI and the PgI/PgII ratio. Similarly, serum gastrin-17 (G-17) levels correlate with the functional status of gastric antral glands [59, 60]. G-17 (an isoform of the hormone gastrin) is specifically synthesized by antral G cells and its plasma levels are significantly reduced in the presence of severe antrum atrophy. On the contrary, G-17 levels are increased in the case of reduced acid output (i.e. severe corpus-mucosa atrophy), and can be used as a hallmark of autoimmune (corpus-limited) atrophic gastritis [61]. The contemporary assessment of serum PgI/PgII and G-17 levels provides the most comprehensive information regarding the overall status of gastric mucosa, being characterized by a significantly higher sensitivity (71 83%) than that of the PgI/PgII ratio alone when used to detect (histologically confirmed) gastric mucosa atrophy 272 Pizzi /Saraggi /Fassan /Megraud /Di Mario / Rugge

9 [61, 62]. Serum PgI/PgII ratio and G-17 levels can thus be used as first-line screening tests for GC secondary prevention strategies. In the setting of H. pylori -related gastritis, normal PgI/ PgII ratio and G-17 levels virtually exclude gastric mucosa atrophy. Patients featuring this serological picture do not need to undergo invasive endoscopic procedures and should only be clinically followed up. Of note, nonatrophic H. pylori- related gastritis can be associated with increased PgII plasma levels, which can be considered as an accessory indicator of the gastritis activity [63]. A reduced PgI/PgII ratio with low (or fairly normal) G-17 levels can be assumed as a marker of corpus-spreading mucosal atrophy, after an earlier atrophic phase limited to the gastric antrum [52, 58]. As atrophic pan-gastritis is widely recognized as a gastric precancerous condition, all patients with H. pylori infection and low PgI/PgII ratio should be considered at increased risk of GC and should undergo endoscopic-histological examination. Based on the results of the invasive tests, different followup strategies can be planned: (a) patients with histologically documented high-olga-stage gastritis should undergo periodical endoscopic follow-up; (b) mild to moderate gastric mucosa atrophy (low OLGA stages) can only be monitored clinically and/or serologically [5, 57]. Conclusions and Future Perspectives Gastric cancer (GC) is the fourth most common malignancy and the second leading cause of cancer-related death worldwide. More than 90% of GC cases occur sporadically and are associated with long-standing inflammatory conditions (mainly H. pylori infection) [64]. The histological assessment of H. pylori-related gastritis provides clinically and prognostically useful information for a patient-tailored follow-up schedule [5]. In the near future, histology-based secondary prevention strategies will be hopefully flanked by new (less invasive and less expansive) procedures, which will enormously enlarge the population of patients suitable for screening of gastric precancerous conditions (particularly in high-risk countries). The PgI/PgII ratio and G-17 levels (together with anti- H. pylori antibodies) represent promising serological biomarkers, and seminal studies indicate their possible role as first-level tests for the identification of high-risk patients eligible for second-level diagnostic procedures. Disclosure Statement The authors declare that no financial or other conflict of interest exists in relation to the content of the article. 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