A Rare Case of Gastric Fundic Gland Adenocarcinoma (Chief Cell Predominant Type)

Gastric adenocarcinoma of the fundic gland type: A review of the literature

Background and Aim

Gastric adenocarcinoma of the fundic gland type (GA-FG) is a newly described tumor entity but lacking consensus. This review summarizes the key features and controversies regarding this uncommon neoplasm.

Methods

We reviewed studies on GA-FG published in English from 2007 to 2021.

Results

We found that 327 cases (340 lesions) have been reported. GA-FG lesions originate from deep layers of the gastric mucosa, with the following characteristics on conventional white-light endoscopy examination. These lesions, macroscopically identified as submucosal tumor-like 0-IIa, tend to have a whitish discoloration without inflammation, atrophy, or intestinal metaplasia in the background mucosa. Tumors located in the upper third of the stomach are usually solitary, with an average size <10 mm. Contrastingly, magnifying endoscopy with narrow-band imaging mostly shows the absence of any demarcation line, with a regular microvascular pattern and regular microsurface pattern. GA-FGs are covered with normal foveolar epithelium, forming a so-called endless glands pattern in the deeper region, which are mainly composed of chief cells or parietal cells. Most tumors exhibit submucosal invasion, but lymphovascular invasion and nodal metastasis are rare. Regarding the treatment of GA-FG, endoscopic submucosal dissection (ESD) and endoscopic mucosal resection (EMR) are effective treatment methods.

Conclusions

GA-FG is a rare tumor that typically follows a benign course. This neoplasm has distinct endoscopic and pathological features and could be treated by ESD or EMR.

Gastric Adenocarcinoma of the Fundic Gland Type: A Case Report

BACKGROUND Gastric adenocarcinoma of the fundic gland type (GAFG) is an extremely rare neoplasm that consists of a mixed proliferation of oxyntic and chief cells. Differential diagnosis of GAFG is difficult in the absence of infiltration. Here, we report a case of GAFG and discuss the clinicopathological features. CASE REPORT A 78-year-old man was diagnosed with gastritis and reflux esophagitis, status after esophagectomy for carcinoma of the esophagus in 2015. The patient underwent repeated gastric biopsies in 2017 and an atypical epithelium was observed, but no diagnosis was confirmed. There was no evidence of tumor extension in the submucosa. The tumor was resected via endoscopic mucosal resection, and pathological examination was performed. Microscopic findings revealed an oxyntic-type gastric mucosa with atypical dense or dilated glands with abundant pale basophilic cytoplasm and round nuclei with prominent nucleoli. The majority of the tumor cells resembled chief cells, suggesting they were derived from gastric fundic glands. However, the tumor appeared to have no submucosal infiltration or focal stromal desmoplastic reaction. Sections stained positive for MUC6 and pepsinogen-I in chief cells, and H+/K+ ATPase and PDGFRa in parietal cells, but were mostly negative for CDX2, chromogranin A, synaptophysin, and CD10. Sections stained for mib-1 expressed very low proliferative activity, with an average of 10%. Staining for TP53 overexpression was negative. CONCLUSIONS Immunostaining markers are a supportive tool for histological diagnosis of GAFG. However, if there is no infiltration, as in our case, it is difficult to consider it as a malignant tumor. Further elucidation is needed in the future, including an officially accepted diagnostic name.

Gastric epithelial neoplasm of fundic-gland mucosa lineage: proposal for a new classification in association with gastric adenocarcinoma of fundic-gland type

BACKGROUND

Gastric adenocarcinoma of fundic-gland type (GA-FG) is a rare variant of gastric neoplasia. However, the etiology, classification, and clinicopathological features of gastric epithelial neoplasm of fundic-gland mucosa lineage (GEN-FGML; generic term of GA-FG related neoplasm) are not fully elucidated. We performed a large, multicenter, retrospective study to establish a new classification and clarify the clinicopathological features of GEN-FGML.

METHODS

One hundred GEN-FGML lesions in 94 patients were collected from 35 institutions between 2008 and 2019. We designed a new histopathological classification of GEN-FGML using immunohistochemical analysis and analyzed via clinicopathological, immunohistochemical, and genetic evaluation.

RESULTS

GEN-FGML was classified into 3 major types; oxyntic gland adenoma (OGA), GA-FG, and gastric adenocarcinoma of fundic-gland mucosa type (GA-FGM). In addition, GA-FGM was classified into 3 subtypes; Type 1 (organized with exposure type), Type 2 (disorganized with exposure type), and Type 3 (disorganized with non-exposure type). OGA and GA-FG demonstrated low-grade epithelial neoplasm, and GA-FGM should be categorized as an aggressive variant of GEN-FGML that demonstrated high-grade epithelial neoplasm (Type 2 > 1, 3). The frequent presence of GNAS mutation was a characteristic genetic feature of GEN-FGML (7/34, 20.6%; OGA 1/3, 33.3%; GA-FG 3/24, 12.5%; GA-FGM 3/7, 42.9%) in mutation analysis using next-generation sequencing.

CONCLUSIONS

We have established a new histopathological classification of GEN-FGML and propose a new lineage of gastric epithelial neoplasm that harbors recurrent GNAS mutation. This classification will be useful to estimate the malignant potential of GEN-FGML and establish an appropriate standard therapeutic approach.

Gastric adenocarcinoma of fundic gland type after Helicobacter pylori eradication: A case report

BACKGROUND

Gastric adenocarcinoma of fundic gland type (GA-FG) has recently been proposed as a novel histological type of gastric cancer.

CASE SUMMARY

We report a case of GA-FG in a 77-year-old Chinese woman with epigastric distention who was referred to endoscopy for the management of an incidentally found submucosal tumor-like elevated lesion in the lower part of the gastric body. The tumor occurred after Helicobacter pylori (H. pylori) eradication therapy without long-term use of proton pump inhibitors. Complete and curable removal of the tumor was performed by endoscopic submucosal dissection. Histopathological findings showed numerous cells with basophilic cytoplasm and mildly atypical nuclei-like chief cells of the fundic gland. The tumor was observed to have the so-called “endless glands” pattern of the well-differentiated mixed phenotype. A safe resection margin without lymphatic and venous invasion was observed. As the tumor occurred after H. pylori eradication therapy, it is unknown whether there was a relationship with H. pylori eradication. The patient will be followed up by periodic gastroscopic observation.

CONCLUSION

In conclusion, we report a case of GA-FG after H. pylori eradication therapy without long-term proton pump inhibitors use. Further analysis of similar cases will reveal the clinical behavior of GA-FG.

Distinct Involvement of the Sonic Hedgehog Signaling Pathway in Gastric Adenocarcinoma of Fundic Gland Type and Conventional Gastric Adenocarcinoma

BACKGROUND/AIMS

Gastric adenocarcinoma of fundic gland type (GAFG), which is a rare variant of gastric cancer, is reportedly associated with both Wnt/β-catenin signaling activation and guanine nucleotide binding protein, alpha stimulating complex (GNAS) mutations. This study aimed to elucidate potential roles of the Sonic hedgehog (Shh) signaling pathway in GAFG.

METHODS

We performed immunostaining for β-catenin and Shh signal-associated proteins, including Patched (Ptch), Smoothened (Smo), and Glioma-associated oncogene-1 (Gli1), and the direct sequencing of GNAS/BRAF/KRAS in 27 GAFGs, and compared them with 30 conventional gastric adenocarcinomas (CGAs).

RESULTS

GAFGs exhibited significantly lower immunoreactivity scores for Ptch, Smo, and Gli1 than CGAs. Moreover, while the Ptch score was significantly lower in the GAFG tumor areas than in the non-neoplastic areas adjacent to GAFG, the score was significantly higher in the CGA tumor areas than in the non-neoplastic areas. Similar trends were observed in the scores for Smo and Gli1. β-Catenin expression and GNAS mutations were found in 22 (81%) and 8 (30%) of the 27 GAFGs respectively. Gli1 expression was significantly associated with mutations in GNAS.

CONCLUSION

GAFG and CGA exhibited distinct Ptch, Smo, and Gli1 expression patterns. Downregulation of the Shh signaling pathway, as well as activation of the Wnt/β-catenin signaling pathway, may therefore be associated with tumorigenesis in GAFG.

Gastric Adenocarcinoma of the Fundic Gland Type: Update and Literature Review

OBJECTIVES

Gastric adenocarcinoma of the fundic gland type (GA-FG) is a newly described entity with a lack of awareness amongst general surgical pathologists and this review highlights the key features and controversies associated with this uncommon neoplasm.

METHODS

A literature search through PubMed using synonyms for GA-FG was conducted to obtain 111 cases.

RESULTS

GA-FG is a well-differentiated neoplasm of oxyntic mucosa, that is comprised of chief cells and parietal cells. Chief cell differentiation is highlighted with Muc-6, RUNX3, and pepsinogen. Parietal cells are highlighted with H+/K+ ATPase and PDGFRA-α. Association with Helicobacter infection, chronic gastritis, intestinal metaplasia, or gastric atrophy is not seen. Most GA-FGs are confined to the mucosa. Deeper invasion, lymphovascular invasion, nodal metastasis, and extragastric spread are uncommon.

CONCLUSIONS

GA-FGs are rare lesions that typically follow a benign course. However, despite features of malignancy in some cases, complete surgical excision, sometimes with endoscopic mucosal resection, seems adequate treatment.

Epigenetic regulation of Wnt/β-catenin signal-associated genes in gastric neoplasia of the fundic gland (chief cell-predominant) type

Gastric neoplasia of the fundic gland (chief cell-predominant) type (GNCCP) is a rare variant of gastric tumor. This tumor is associated with activation of the Wnt/β-catenin signaling pathway; however, the mechanisms underlying this activation remain unknown. To elucidate potential roles of Wnt/β-catenin signal-associated gene methylation in GNCCP, we performed β-catenin immunostaining and methylation-specific polymerase chain reaction (PCR) for their associated genes, including SFRPs, APC, AXIN2, and MCC, in 26 GNCCPs [i.e., 11 intramucosal (GNCCP-Ms) and 15 submucosal tumors (GNCCP-SMs)], and compared with 27 fundic gland polyps (FGPs), 12 FGPs with dysplasia (FGP-Ds), 27 conventional gastric adenocarcinomas (CGAs). Nuclear β-catenin labeling indices were higher in GNCCPs and CGAs than in FGPs and FGP-Ds. SFRPs, APC, and AXIN2 were more frequently methylated in GNCCPs and CGAs (SFRP1, 88%/96%; SFRP2, 85%/93%; SFRP4, 73%/81%; APC, 81%/81%; AXIN2, 81%/85%; respectively) than in FGPs and FGP-Ds (37%/50%; 41%/42%; 41%/58%; 37%/33%; 41%/50%; respectively). A significant correlation was seen between nuclear β-catenin expression and methylation of SFRP1 in GNCCPs. Furthermore, nuclear β-catenin expression was significantly frequent in high-methylated GNCCPs than in low-methylated tumors. In conclusion, our results suggest that activation of this pathway, mediated by gene methylation, may be associated with progression of some GNCCP cases, similar to CGAs.

Chief cell-predominant gastric polyps: a series of 12 cases with literature review

AIMS

Rare gastric lesions composed of a combined proliferation of chief and oxyntic cells have been variably called adenocarcinoma of fundic gland type and oxyntic gland polyp/adenoma. Herein, we present a series of cases that show a morphological spectrum of chief and oxyntic cell proliferations.

METHODS AND RESULTS

Routine and consultation cases were collated from five institutions. Information regarding site, size, endoscopic appearance, clinical history and medication use, when available, was accrued, as was the histological features and immunoprofiles. A total of 12 cases were collated. Age ranged from 39 to 81 years. All the lesions were located in the fundus; seven of eight were polypoid lesions endoscopically. Lesions were primarily solitary, averaged 4.6 mm in diameter (largest 9 mm) and comprised >50% chief cells. The predominant architectural pattern was of anastomosing and solid and clustered glands or a mixture of these patterns. Lesions were limited mainly to the mucosa, although two showed submucosal involvement. None had known metastatic disease.

CONCLUSIONS

This series included lesions that were previously described as gastric adenocarcinoma of fundic gland type and oxyntic gland polyp/adenoma. They are located exclusively in the fundus and composed predominantly of chief cells with low-grade cytology and appear to show a morphological continuum.

Mutation spectrum in the Wnt/β-catenin signaling pathway in gastric fundic gland-associated neoplasms/polyps

Frequent activation of the Wnt/β-catenin signaling pathway has recently been demonstrated in gastric adenocarcinoma/neoplasia of chief cell predominant type (GA-CCP/GN-CCP) with submucosal involvement. In this study, we examined the activation status of the Wnt/β-catenin signaling pathway in GN-CCP without submucosal involvement, which is referred to as gastric dysplasia-CCP (GD-CCP). We also examined β-catenin expression and the mutation spectrum of PPP2R1A and Wnt pathway genes in 11 cases of GD-CCP, 25 cases of gastric polyps of fundic gland type (GPs-FG), and 21 cases of GPs-FG with dysplasia (GP-FGD). β-catenin nuclear staining was observed in 3 cases of GD-CCP, none of GPs-FG, and 6 cases of GPs-FGD. Mutations in Wnt pathway genes, including PPP2R1A, were observed in 4 cases of GDs-CCP, 10 cases of GPs-FG, and 7 cases of GPs-FGD. Two of these seven GPs-FGD cases showed β-catenin nuclear staining. However, none of the 4 GD-CCP cases with mutations or the 10 GPs-FG cases with mutations showed β-catenin nuclear staining. PPP2R1A mutations were observed in 1 GD-CCP case and 1 GPs-FGD case. Although the mutation spectra of the Wnt pathway genes in GD-CCP and GP-FG differed, based on the absence of β-catenin nuclear staining despite the genetic alterations, GD-CCP is more similar to GP-FG than to GN-CCP, which shows β-catenin nuclear staining and submucosal involvement. Activation of the Wnt/β-catenin signaling by the β-catenin nuclear transition may be required during progression from GD-CCP to GN-CCP. Furthermore, this is the first report describing PPP2R1A mutations in gastric fundic gland-associated neoplasms.

GNAS mutation as an alternative mechanism of activation of the Wnt/β-catenin signaling pathway in gastric adenocarcinoma of the fundic gland type

Gastric adenocarcinoma of the fundic gland type (GAFG) is a rare variant of gastric tumor. We have recently reported the frequent accumulation of β-catenin in GAFGs and showed that approximately half of the cases studied harbored at least 1 mutation in CTNNB1/AXINs/APC, leading to the constitutive activation of the Wnt/β-catenin pathway. However, the mechanisms of Wnt signaling activation in the remaining cases are unknown. Accumulating evidence showed that the activating mutation in GNAS promotes tumorigenesis via the activation of the Wnt/β-catenin pathway or the ERK1/2 MAPK pathway. Therefore, we analyzed the mutations in GNAS (exons 8 and 9) and in KRAS (exon 2) in 26 GAFGs. Immunohistochemistry revealed nuclear β-catenin expression in 22 of 26 GAFGs, and 10 (38.5%) of 26 cases harbored at least 1 mutation in CTNNB1/AXINs/APC. Activating mutations in GNAS were found in 5 (19.2%) of 26 GAFGs, all of which harbored R201C mutations. Activating mutations in KRAS were found in 2 (7.7%) of 26 GAFGs, and both of these also contained GNAS activating mutations. Four of 5 cases with GNAS mutation showed nuclear β-catenin expression, and presence of GNAS mutation was associated with β-catenin nuclear expression (P = .01). Furthermore, 3 of these 4 cases did not harbor mutations in CTNNB1, APC, or AXINs, suggesting that mutations in the Wnt component genes and those in GNAS occur almost exclusively. These results suggest that GNAS mutation might occur in a small subset of GAFG as an alternative mechanism of activating the Wnt/β-catenin signaling pathway.

Alteration in the Wnt/β-catenin signaling pathway in gastric neoplasias of fundic gland (chief cell predominant) type

Gastric neoplasia of chief cell-predominant type (GN-CCP) has been reported as a new, rare variant of gastric tumor. GN-CCPs were defined as tumors consisting of irregular anastomosing glands of columnar cells mimicking chief cells of fundic gland with nuclear atypia and prolapse-type submucosal involvement. We comparatively evaluated clinicopathologic features between 31 GN-CCPs and 130 cases of conventional gastric adenocarcinoma invading into submucosa (CGA-SM) in addition to nuclear β-catenin immunolabeling and direct sequencing of members of the Wnt/β-catenin pathway, CTNNB1, APC, and AXIN, in a subset of these tumors. GN-CCP presented as small protruded lesions located in the upper third of the stomach, with minimal involvement into the submucosa and rare lymphovascular invasion. None of the lesions have demonstrated a recurrence of disease or metastasis on follow-up. Nuclear β-catenin immunolabeling was higher in GN-CCP (labeling index [LI]: median, 19.3%; high expresser [LI >30%], 7/27 cases [26%]) than CGA-SM (median LI, 14.7%; high expresser, 1/19 cases [6%]). Missense mutation of APC was observed in 1 GN-CCP but not CGA-SM. Missense or nonsense mutations of CTNNB1 and AXIN1 were higher in GN-CCPs (14.8%, both) than CGA-SMs (5.3%, both). Missense mutations of AXIN2 were higher in GN-CCPs (25.9%) than in CGA-SMs (10.5%). Overall, 14 (51.9%) of 27 GN-CCPs and 5 (26.3%) of 19 CGA-SM cases harbored at least 1 of these gene mutations. In conclusion, GN-CCPs as a unique variant of nonaggressive tumor are characterized by nuclear β-catenin accumulation and mutation of CTNNB1 or AXIN gene, suggesting activation of the Wnt/β-catenin pathway.