胃分化型SM1癌（垂直浸潤500μm未満）の診断―500μm以上と対比して―ひだ集中のない陥凹型胃癌に対するX線診断

Radiological Diagnosis of the Depressed Type of Gastric Submucosal Cancer Without Fold Convergence―Based on the Vertical Invasive Depth of a Differentiated-type Submucosal Cancer

要旨　目的：分化型SM胃癌の垂直距離からみたX線的な描出能や組織学的な特徴を明らかにする．対象と方法：ひだ集中のない陥凹型pSM癌70病変を対象とし，X線・組織所見を対比検討した．結果：①pSM1癌とpSM2癌の臨床病理学的な差異：pSM1癌に比べpSM2癌は，中分化型主体，0IIc＋IIa型を呈し，リンパ管侵襲率が有意に高かった．②SM垂直距離からみた5つの撮影手技単独のX線的描出感度：いずれの撮影手技も描出（＋）群はほとんどが500μm以上のpSM2癌であった．描出（－）群は垂直距離にばらつきが認められ，撮影手技単独による描出の限界が示唆された．③SM垂直距離別にみた総合的なX線的描出感度：5つの撮影手技を駆使した場合，1,000μm以上あれば描出感度は90％と良好であった．しかし，500μm未満ではほとんど描出不能で，500～999μmは50％と不良であった．④SM垂直距離別にみたSM癌巣の組織学的な特徴：500μm未満は，Mとの厚さの比：M＞SM，SM水平距離：5mm未満，Mとの幅の比：M＞＞SM，SM発育分布形式：点状，線維形成反応：なし～軽度，粘膜筋板の状態：保持～部分断裂がほとんどを占め，SM癌巣の厚さ・硬さに関連する組織因子に乏しく，1,000μm以上と深いほど著明であったことが，描出感度の差の要因と思われた．結論：SM癌巣の組織学的な特徴の違いから，X線的に良好な描出が得られる垂直距離は1,000μm以上で，今後は500～999μmに対する診断能向上が必要である．

　Aim : To clarify the radiological diagnostic ability of depressed type gastric submucosal (pSM) cancer without fold convergence. Material and method : 70 differentiated-type cancer specimens obtained by surgery or endoscopic resection were employed for the studies concerning the following, based on the vertical depth of submucosal invasion. Results : (1) There were significant clinico-pathological differences between the pSM1 (less 500μm) and the pSM2 (over 500μm) cancer in vertical invasive depth, intramucosal histological type, macroscopic type, and lymphatic invasion. (2) Radiological diagnostic ability of each of five different techniques : Positive findings included cancers with over 500μm of vertical invasion. Negative ones were numerous in those cancers with less than 500μm of invasion, but variable in vertical invasive depth. (3) Overall radiological diagnostic ability : When vertical invasion was more than 1,000μm, 90％ positive findings were obtained by five different radiographic techniques. Cancers with less than 500μm of invasive depth were almost impossible to identify positively, but 50％ of 500～999μm lesions were identified positively. (4) Histological characteristics of pSM cancer : In the lesions with less than 500μm vertical invasion, histological factors related to the tumor thickness and sclerosis were not reflected on the radiography, but it was prominent in lesions with more than 1,000μm of submucosal invasion. This was the major cause of difference in radiographic diagnosis between the pSM1 and pSM2 cancers. Conclusion : It is difficult to reveal pSM1 cancer by radiographic studies. Diagnosis of pSM2 cancer can be made by radiography. Hereafter, pSM cancer with 500～999μm of vertical invasion is a target lesion for improvement radiographic means of diagnosis.