小胃癌の深達度診断―X線診断について

Radiological Diagnosis of the Invasivity of Small Gastric Cancers

要旨　内視鏡的治療の対象となる早期胃癌，すなわち2cm以下で粘膜ひだ集中のない分化型のⅡcのX線的深達度診断について，症例を挙げ，そのX線所見を中心に検討した．症例は男性46例，女性15例，の計61例で，平均年齢は58.8歳，粘膜内癌（m癌）48例，粘膜下層まで浸潤した癌（sm癌）13例であった．陥凹と陥凹の辺縁隆起に注目し，X線所見を6群に分けて検討した．浅い不整形陥凹で陥凹底が細顆粒状の陥凹ではm癌が多く，不整形で陥凹底が平滑なものでは5例中2例はsm癌であった．深いはっきりした陥凹を示した例は14例あったが，そのうち11例はm癌であった．陥凹の辺縁隆起が花弁状のものは分化型癌の特徴的な1群で深達度はm癌であった．その他の辺縁隆起には顆粒状，結節状のものがあり，これらの所見を示した21例中7例がsm癌であった．これらの辺縁隆起は種々の構成成分からなり，必ずしもsm浸潤を示す所見とは言えなかった．深達度診断は病変の占拠部位，大きさ，潰瘍の合併の有無，組織型などを加味して行われる．この症例を絞る過程でもX線診断は大きな役割を果たしている．

　It is necessary to make a precise evaluation of invasivity to determine the likelihood of success of endoscopic surgery such as endoscopic mucosal resection. Type Ⅱc differentiated carcinomas less than 2 cm in size without mucosal coverging folds are often resected in this fashion. Their invasivity were analyzed from the radiological diagnostic point of view.

　The average age of 61 cases (46 male and 15 female) was 58.8 years old. Forty eight of them were mucosal cancers and 13 of them were submucosal.

　The radiological findings of these lesions were classified into six groups (A-F) based on shape of the depression, floor of the depression and marginal elevation. Group A (an irregular and shallow depression with a granular appearance of the floor) was mostly mucosal cancer. Two out of 5 cases of group B (an irregular and shallow depression with a flat floor) were submacosal. The invasivity of group C was not associated with the radiological depth of depression. All lesions in group D (an irregular and shallow depression with petal-like elevation) were diagnosed as mucosal cancer. This type of depression was common in type Ⅱc differentiated cancer. Seven of the 21 lesions in group E and F (a granular and nodular marginal elevation) were submucosal cancer. The marginal elevation of lesion did not always mean submucosal cancer, because it consisted of various histological components.

　Radiologically, it is very difficult to evaluate the invasivity of minute submucosal infiltration of cancer cells. Before estimating the local morphological findings, it is necessary to ascertain the localization, size and histological type of the lesions. Radiological diagnosis will play an important role in obtaining such information, and helps in making a precise evaluation of the invasivity of cancer.