內視鏡超音波臆測小型胃部胃腸基質瘤之臨床病理評估

Abstract

胃腸基質瘤（Gastrointestinal stromal tumor, GIST）是常見的胃表皮下腫瘤。目前內視鏡超音波被廣泛利用於評估胃表皮下腫瘤，而內視鏡超音波對於診斷胃腸基質瘤也有頗佳的敏感度。當例行性內視鏡檢查意外發現胃表皮下腫瘤的情形愈來愈多，在後續內視鏡超音波臆測為小型胃腸基質瘤的機會也就愈高。然而現今美國國家癌症資訊網（NCCN）治療建議對於小型胃部胃腸基質瘤（小於2公分）的處置仍有爭議，也沒有前瞻性的研究來認可現行以內視鏡超音波進行規則追蹤的策略。 在之前的回溯性研究，以50個小於3公分的內視鏡超音波臆測胃部胃腸基質瘤的病患為研究對象，發現大於1.4公分的內視鏡超音波臆測胃部胃腸基質瘤較會在追蹤過程中持續進展增大。另外，小型胃部胃腸基質瘤之腫瘤增長相關的重要因子，包括了腫瘤的初始尺寸及不規則的腫瘤邊緣。這類內視鏡超音波臆測胃部胃腸基質瘤研究，因為小型表皮下腫瘤組織取樣不易，無法有完整的組織診斷為胃腸基質瘤，所以結論推估上有著一定的限制。此外，考慮到一般常被論述的「組織增生－腫瘤贅生」時序性，小型胃腸基質瘤被視為自我限制生長能力的良性病灶，還是已經算是惡性胃腸基質瘤的發展早期，現階段仍有爭議。此研究的目標有兩個，其一在於試圖找出較佳且安全的診斷策略，以提高小型胃腸基質瘤的組織診斷率；其二在於前瞻性的驗證這類小型胃腸基質瘤中病理與分子的特徵。我們期待這些研究上的努力，能夠為小型胃腸基質瘤建立更好的處置流程。

Gastrointestinal stromal tumors (GISTs) account for the largest proportion of gastric subepithelial tumors (SETs). Endoscopic ultrasound (EUS) is widely used for evaluating gastric SETs, and is sensitive to detect those locate at the fourth layer, name as EUS-suspected gastric GISTs. Since screening endoscopy becomes common, more SETs are discovered and the incidence of EUS-suspected gastric GISTs are increasing. Under current National Comprehensive Cancer Network (NCCN) guidelines, the management of small GISTs with size less than 2 cm remains controversial. There is also no prospective study to assess the interval of EUS surveillance of small GIST. In a retrospective study, 50 patients with EUS-suspected gastric GISTs of sizes less than 3 cm were followed up by EUS at least twice over a period of more than 24 months, subgroup larger than 1.4cm was associated with significant progression. Other important factors of tumor progression include initial tumor size and irregular tumor border. Due to challenging tissue acquisition and lack of definite pathological diagnosis, current studies about EUS-suspected gastric GISTs have limitations. Concerning possible hyperplasia-neoplasia sequence, whether small GISTs are considered as self-limiting benign lesion or pre-malignant lesion are still under debate. The aims of our study are to (i) validate the endoscopic incisional biopsy as an alternative and safe method for diagnostic yield of small fourth layer subepithelial tumors, particularly GISTs, (ii) study the pathologic and molecular characteristics of small gastric GISTs prospectively.