Histological diagnosis of gastric subepithelial tumors is difficult. Endoscopic biopsy often fails to obtain adequate tissue from the deep layer of the stomach. EUS offers an alternative modality for diagnosis by showing its layer of origin, shape, border, size, and texture echogenicity. These parameters have been shown to predict its malignant potential of a GIST, with a sensitivity of 83%-86% and a specificity of 76%-80%
]. In addition, EUS-guided fine needle aspiration for cytology (FNAC)
] or Tru-cut biopsy
] provides sufficient tissue for histopathological and immunohistochemical diagnosis. Polkowski et al.
] reported a diagnostic yield of 67% (0%-94%) by EUS-FNAC, and 91% (87%-100%) by EUS-guided biopsy. However, calculation of mitotic index remains difficult using tissue core obtained from either needles, and sampling bias further confounds the interpretation.
With recent advent of endoscopic resection techniques, endoscopists can now remove mucosal or submucosal tumors by endoscopic mucosal resection (EMR)
]. Yet complete resection of subepithelial tumors larger than 2
cm in size and those originating from the muscularis propria layer remain difficult by EMR. Recently, ESD has been introduced for treatment of early cancers of gastrointestinal tract
]. It allows complete resection of superficial lesions irregardless of their size. With the development of endoscopic resection techniques and devices, endoscopic treatment for tumors originating from the muscularis propria became possible. Park et al.
] first demonstrated endoscopic enucleation of esophagogastric subepithelial tumors using IT-knife. Fourteen of the 15 (93.3%) subepithelial tumors were successfully resected. Of these tumors, eleven originated from the muscularis propria layer and 5 were GISTs. Shim et al.
] described several tools for ESD with enucleation of subepithelial tumors originating from the muscularis propria layer, including electrosurgical snare, cutting knife and IT-knife. Lee et al.
] achieved successful resection of 9 out of 12 gastric subepithelial tumors originating from the muscularis propria layer by IT-knife, while the remaining 3 were partially removed by EMR with a cap. GIST with low malignant potential was diagnosed in 8 cases and leiomyoma in 4 cases. In our study, fifteen of the 16 subepithelial tumors were resected completely in one piece by using a modified ESD with enucleation. The resection technique in this study was similar to that by Park et al.
]. But instead of making a longitudinal incision alone, an additional transverse incision to the lateral sides of the tumor was made. This additional incision, like orange peeling, exposes the tumor and its underlying muscularis propria layer more clearly, so that complete dissection of the tumor can be more easily performed. The only tumor that could not be completely resected was the largest one of 42
mm in size, due to its wide contact area with the underlying muscularis propria layer, this patient received surgical treatment. The location of the tumor is a point of concern when performing this procedure. More time was consumed for resection of the tumor in the fundus than those in the body or the antrum. This is because retroflexion of the endoscope brings the IT knife 2 vertically oriented to the muscularis propria layer, dissection is more difficult as a result. In our case, we used the technique of polypectomy instead by employing an electrosurgical snare in the final step of tumor resection successfully. All the GISTs we removed were encapsulated which allowed complete dissection. Pathological examination at low-power field confirmed the presence of an intact and thin fibrous capsule (Figure
Figure 3 Pathology of GIST after ESD with enucleation. a. A well-defined tumor surrounded by a thin capsule (Hematoxylin-eosin, 1x). b. A spindle cell tumor surrounded by fibrous tissue (Hematoxylin-eosin, 400x). c. The tumor cells are positive for c-Kit with (more ...)
The two common ESD-related complications are perforation and bleeding. Perforation risk following endoscopic resection of subepithelial tumors originating from the muscularis propria layer has been estimated from 0-28%
]. The most common location of perforation is the fundus. Nevertheless, most of the perforations are small and can be successfully managed by endoscopic application of hemoclips and without need for surgical intervention. Most of the studies reported, no overt bleeding during endoscopic resection. In this study, there was a high success rate (15/16) for complete resection by the modified ESD with enucleation we introduced. No procedure-related perforation or overt bleeding occurred. Minor bleeding during the procedure was common but adequate hemostasis was always achieved. Epigastric pain was usually mild.
In Miettinen’s series, the size of GIST is between 2 and 5
cm, there is a 1.9% of tumor-related mortality or distant metastasis when mitotic index is less than or equal to 5 mitosis per 50 HPFs, and a 16% when mitotic index is higher than 5 mitosis per 50 HPFs
]. Most of the gastric subepithelial tumors in our series were GISTs (14/16), their size ranges from 2 to 5
cm and they all had mitosis index of less than 5 per 50 HPFs. We followed our patients for a mean duration of 14.8
months. There was no local recurrence or distant metastasis. However, long-term follow-up is suggested.
In conclusion, we introduce a modified ESD with enucleation for complete resection of gastric subepithelial tumors originating from the muscularis propria layer and larger than 2
cm. This procedure preserves the integrity of the stomach and shortens hospital stay. It is a safe and effective alternative to surgical therapy.