超音波内視鏡による胃平滑筋腫瘍の良･悪性鑑別診断

Diagnosis of Gastric Myogenic Tumor by Endoscopic Ultrasonography

要旨　手術で確定診断が得られた平滑筋腫瘍44例45病変のEUS所見を検討し，以下の結論を得た．①EUSによる内部エコー像は，病理組織所見をよく反映し，高エコー域は滲出液の小さな貯溜，最小血管腔，小さな出血巣の混在に，無エコー域は，滲出液やフィブリン析出物の大きな貯溜，大きな血管腔による囊胞様構造物に相当した．②EUS上，A型（均一低エコー型）は平滑筋腫，B型（高エコー域混在型），C型（高エコー域，無エコー域混在型）は平滑筋肉腫危険群であり，高エコー域の混在が悪性を示唆する重要な所見であった．③EUSによる経過観察例において，内部エコー像の変化，および急速な発育は悪性を示唆した．④以上，EUSは胃平滑筋腫瘍の良・悪性の鑑別に有用と考えられた．

　Preoperative endoscopic ultrasonography (EUS) examination was performed in 44 patients with 45 gastric myogenic tumors who underwent gastrectomy from 1986 to 1994. A study of the efficacy of EUS for distinguishing leiomyosarcoma (18 patients with 18 tumors) from leiomyoma (26 patients with 27 tumors) was carried out. In this study, we classified gastric myogenic tumors into three types based on the internal echoic pattern shown by EUS. Type A consisted of tumors whose internal echoic pattern was hypoechoic and homogeneous. Type B, on the other hand, was comprised of tumors whose internal echoic pattern was a mixture of hypo-and hyperechoic patterns. Type C consisted of tumors whose internal echoic pattern was a mixture of hypo-and hyperechoic patterns with an echoic area. The results were as follows:

　1) EUS findings corresponded precisely to the histological findings (Table 3).

　2) The tumors with type A internal echoic pattern were consistent with leiomyoma, and those with type B or type C internal echoic pattern were suspected to be leiomyosarcoma (Table 3, Fig. 4). The mixture of hypoand hyperechoic patterns as detected by EUS were thought to be signs of malignancy.

　3) The change of internal echoic pattern or rapid growth as detected by EUS were thought to be signs of malignancy (Table 4, Fig. 5).

　4) EUS was useful for differentiating gastric leiomyosarcoma from leiomyoma.