RM-066 Histological diagnosis of gastric submucosal tumors after endoscopic submucosal dissection

Abstract

Introduction: Gastric submucosal tumors (SMTs) such as gastrointestinal stromal tumor (GIST), leiomyoma, leiomyosarcoma, schwannoma, glomus tumor and non-neoplastic lesions such as inflammatory fibroid polyp, heterotopic pancreas and more are frequently identified during routine upper endoscopies. Endoscopic ultrasonography (EUS) is one of the most useful modalities for diagnosing gastric SMTs. However, it is usually not possible to differentiate GIST from benign conditions such as leiomyoma or schwannoma by EUS, especially when the tumor originated from the muscularis propria layer. There are several similar methods for the histological diagnosis of SMTs: mucosal cutting biopsy (MCB), a mucosal incision-assisted biopsy technique, and an “unroofing” biopsy based on endoscopic mucosal resection (EMR). Endoscopic submucosal dissection (ESD) is an advanced endoscopic therapy for SMTs and ESD has rapidly become widely used. Histological diagnosis of the removed tumor is important for the further tactics and prognosis. Methods: We undertook a retrospective review of the 21 patients with gastric SMTs who underwent ESD in our hospital “Oberig clinic” (Kyiv, Ukraine) between January 2009 and December 2015. All patients underwent EUS before the procedure (Olympus EUS EXERA EU-M60, UM DP20-25R). Written informed consent was obtained from all patients. ESD were performed by one experienced endoscopist. (Olympus Exera II, GIF Q-160Z; Olympus Exera III, GIF HQ-190). Results: The patients included 8 men and 13 women with a median age of 57 years (range: 33–67 years). On EUS, 17 tumors (81%) were located in the submucosal layer and 4 (19%) in the muscularis propria layer. Median tumor size was 10 mm (range: 4–35 mm). The tumor sizes were ≤ 20 mm in 17 lesions (86%) and > 20 mm in 4 (14%). Paraffin-embedded resected specimens were sectioned and stained with hematoxylin and eosin. If needed, additional immunohistochemical staining for c-kit (CD117), DOG-1, CD34, desmin, smooth muscle antigen (SMA), or S-100 protein was performed to differentiate tumors of mesenchymal origin. Mesenchymal lesions that stained positive for SMA and desmin were diagnosed as leiomyomas. Lesions that stained positive for c-kit or DOG-1 and CD34 were diagnosed as GISTs. Lesions that stained positive for S-100, chromogranin A, neuron-specific enolase were diagnosed as neuroendocrine tumors. The malignant potential of GISTs was categorized based on tumor size and mitotic counts with Phospho-Histone H3 (mitotic marker), and malignant potential of neuroendocrine tumors was determined with Ki-67. The histological diagnoses were neuroendocrine tumor (n = 7), GIST (n = 5), leiomyoma (n = 4), inflammatory fibrinoid polyp (n = 2), glomus tumor (n = 1), calcifying fibrous tumour (n = 1), aberrant pancreas (n = 1). Conclusion: The final histopathological diagnosis for most gastric SMTs tumors is only possible after the immunohistochemical study. The ESD is an effective, safe, and feasible treatment for gastric SMTs, which can resect the whole lesion and provide pathological information.