The role of endoscopy in the diagnosis of gastric gastrointestinal stromal tumors.

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Gastrointestinal stromal tumor (GIST) is a rare cancer but the most common sarcoma in the gastrointestinal tract, arising most frequently in the stomach. 1 Its clinical incidence is estimated to be 10 million/year. The standard treatment of primary and localized GIST is macroscopically complete resection. Gastric GIST shows significantly better prognosis after surgery than non-gastric GIST. GIST is considered to be originated from mesenchymal cells potentially differentiating into the interstitial cells of Cajal and mostly occurs in the intermuscular layer. 1,2 Subsequent progression of GIST may be intraluminal, extrinsic, or bidirectional in the gastric wall. Practically, all tumors are covered by the normal mucosa and appear as submucosal (or subepithelial) tumors (SMTs) in endoscopic and fluoroscopic examinations. Hence, GIST is not directly visualized by endoscopy without using endoscopic ultrasound (EUS), and pathological specimens are not always obtained by conventional endoscopic biopsy. Because of its neoplastic behavior and localization, GIST may be sometimes asymptomatic until advanced stages and its histologic diagnosis prior to surgery is still challenging. The confronting problems include distinguishing the tumors with malignant behaviors and courses, which require treatment, from those with benign ones, which afford a watch-and-wait approach. Endoscopy is of demonstrated value in diagnosis of esophageal and gastric carcinomas by identifying lesions and by providing tumor specimens for pathological examinations. In GIST and SMT, however, its diagnostic significance is not yet established. In this issue of the Annals of Surgical Oncology, Park et al. have shown some clear evidences for diagnostic roles of endoscopy and limitations of endoscopic examinations. 3 Using the data obtained from their retrospective analysis of patients with histologically confirmed gastric GISTs, they shows that GISTs detected by periodical endoscopy are smaller in size, fewer in ulceration, and less symptomatic than those without periodical endoscopy when they show intraluminal growth, although endoscopy has a limited role in diagnosis of GISTs showing extrinsic growth. Alternatively, their data suggest that CT may work for extrinsic tumor and/or huge tumor [10 cm as an initial diagnostic approach. In fact, CT and MRI are proposed as a first choice to study location and extension of GIST in the guidelines. 4 The other multicenter retrospective study has shown the alternative view that the patients with GISTs detected by gastric cancer screening without symptoms were smaller in size and better in prognosis than those with symptomatic GISTs. 5 Taken together, periodical endoscopy may facilitate early detection of gastric GISTs before episodes, which may result in potential improvement in the prognosis of patients with gastric GISTs, although there may be leadtime bias.