Although several reports have addressed the various treatments of GHIP, such as ESD, gastrectomy, laparoscopic wedge resection, or LECS [4, 5, 9, 10], to the best of our knowledge, this is the first case of GHIP that was diagnosed and treated using modified CLEAN-NET.
GHIP is rare, making up for less than 1% of all gastric polyps [11, 12]. It is pathologically defined by the inverted growth of the hyperplastic gastric mucosal components into the submucosa and smooth muscle located in the submucosal layer, with branching from the proliferation of smooth muscle bundles [13, 14]. In the present case, we confirmed such findings by pathological examination, including immunohistochemical staining. GHIP is thought to occur due to the infiltration of the mucosa through muscularis mucosa cracks or defects caused by repeated erosion . There are two types of hamartomatous inverted polyps: SMT type, as in the present case, which does not have a stalk; and polyp type, which has a stalk .
GHIP is usually asymptomatic and tends to be found incidentally, despite occasionally manifesting as an intestinal obstruction or as anemia secondary to chronic blood loss . It sometimes develops into an SMT of more than 2 cm in diameter or an SMT with a central dimple. Ueo et al. reported that the observation of the multilocular anechoic region in the third layer of the gastric wall in endoscopic ultrasound (EUS) examination might be suggestive of GHIP . This feature could distinguish GHIP from other SMT like GIST. However, other features of EUS imaging also have been reported, such as diffuse hyperechoic mass located in the submucosal layer ; thus, it is impossible to diagnose GHIP by EUS alone. In this case, a heterogenous tumor with cystic spots was shown by EUS but its location in gastric wall layers was unclear, while we were not familiar with its image of EUS. Thus, we could not diagnose the SMT as GHIP by EUS before resection. In contrast, endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) was not performed in this case. However, even though the tissue is taken correctly, making an accurate diagnosis is difficult because the foveolar epithelium of the GHIP can be misdiagnosed as gastric mucosal epithelium . Previous studies also reported that it was difficult to diagnose before resection because of its inverted growth into the submucosal layer, as well as the paucity of previous case reports [4, 14].
GHIP is a benign tumor; however, there have been reports on GHIP that contained gastric cancer. Although its occurrence is very low, and the association of GHIP with carcinogenesis is controversial, it should be considered [5, 6]. In addition, it is reported that GHIP sometimes has a central dimple as admitted on GIST [4, 7]. In our case, a central dimple was also admitted. We suspected the tumor as GIST. Thus, an en bloc resection was needed for both the diagnosis and treatment of the tumor. Therefore, in the present case, it was important not only to resect the tumor completely and perform a less invasive diagnosis and treatment, but also to prevent tumor dissemination. We therefore conducted modified CLEAN-NET.
Original CLEAN-NET, which was first reported by Inoue et al. in 2012, is one of the modified LECS procedures. The technique preserves the mucosal layer, which provides a mechanical barrier between the gastric lumen and the peritoneal cavity. Therefore, it can avoid intraoperative tumor dissemination and exposure to the content of the stomach [8, 19]. Non-exposed endoscopic wall-inversion surgery (NEWS) is also a non-exposure technique among modified LECS procedures . However, since the tumor is retrieved orally in NEWS, as with ESD, it can only be used for tumors sized < 3 cm. On the other hand, original CLEAN-NET can be performed for tumors sized ≥ 3 cm, because the tumor is removed transabdominally; however, the risk of deformation of the remnant stomach is high when the tumor size is large .
In contrast, there are limitations to CLEAN-NET. Resection of a tumor located adjacent to the esophagogastric junction (EGJ), the pyloric ring, or the lesser curvature is sometimes technically demanding, because the likelihood of the occurrence of postoperative stenosis caused by deformity of the stomach is higher in these locations. In addition, a tumor located on the posterior wall was also reported to be difficult to remove by CLEAN-NET, due to its inaccessibility . Fujishima et al. reported a modified CLEAN-NET technique, modifying the resection and closure procedure using laparoscopic stapling devices from full-layer stapling to only mucosal layer and adding seromuscular closure by handsewn suturing. This technique enabled resect the gastric SMTs near the EGJ or the pyloric ring without any stenosis . In our case, the tumor was over 3 cm and located at the posterior wall near the cardia of the stomach. Thus, we selected modified CLEAN-NET and could remove the tumor with little deformation of the stomach relatively easily by using anchor sutures around the tumor to secure the surgical field.
Modified CLEAN-NET is one of the potential treatment modalities for GHIP, in terms of conducting en bloc resection because it avoids dissemination, is minimally invasive, and has a reduced chance in resulting in deformity of the stomach.