小さな未分化型胃癌の内視鏡診断の実態

Endoscopic Diagnosis of Minute and Small Undifferentiated type Early Gastric Carcinoma

要旨　小さな未分化型早期胃癌は臨床発見がまれとされている．そこで，仙台市医療センターで外科的，内視鏡的に切除された早期胃癌1,912病巣を，EMRが確立される以前の前期（1980～1990年）と確立された後の後期（1991～1995年）に分け，未分化型微小・小胃癌の診断の実態を比較検討し，更に臨床病理学的特徴，内視鏡的特徴を抽出した．その結果，①未分化型微小胃癌は8病巣，同小胃癌は26病巣であった．②微小・小胃癌に占める未分化型の頻度は，微小胃癌では前期で5％，後期で7％，小胃癌では前期で12％，後期で9％と，前期，後期ともに低かった．また，未分化型早期胃癌の大きさ別分布をみると，前期，後期ともに10mmを超えて発見頻度が急増しており，未分化型微小・小胃癌が見逃されている可能性が示唆された．③臨床病理学的特徴をみると，未分化型微小胃癌・小胃癌ともに，M領域のⅡc型が多かった．また，未分化型癌は小胃癌になるとUlを伴いやすい傾向があった．④内視鏡的特徴をみると，未分化型微小胃癌・小胃癌ともに，発赤顆粒を伴う褪色陥凹が重要な指標であった．以上，小さな未分化型早期胃癌を見逃さないためには，M領域の発赤顆粒を伴う褪色小陥凹に注意することが重要であった．

　Objectives : We conducted this study to clarify the clinicopathological and endoscopic characteristics of minute (5 mm or less in diameter) and small (10 mm or less in diameter) undifferentiated type early gastric carcinoma.

　Patients and methods : There were 1,912 early gastric cancer lesions in 1,661 patients who underwent gastrectomy or endoscopic mucosal resection (EMR) in the 16-year period from 1980 to 1995. The patients were divided into two groups. One group consisted of patients who had undergone gastrectomy from 1980 to 1990, during which time, EMR had not yet been established at our institution. The other group was comprised of patients treated from 1991 to 1995 who received EMR or gastrectomy in accordance with indications for the use of the EMR procedure which had, by that time, been established at our institution. Using these cases, we reviewed clinicopathological findings and endoscopic diagnosis of small undifferentiated type early gastric cancers.

　Results : 1) In the earlier period, there were four minute lesions and 13 small lesions of undifferentiated type early gastric cancer, which accounted for 5% of minute and 12% of small early gastric cancers. In the later period, there were four minute lesions and 13 small lesions of undifferentiated type early gastric cancer, which accounted for 7% of minute and 9% of small early gastric cancers. Undifferentiated type early gastric cancers were frequently 10 mm to 20 mm in diameter (31% in the earlier period and 35% in the later period). This suggests that minute and small undifferentiated type early gastric cancers had been overlooked. 2) Clinicopathologically, seven minute lesions (87%) and 18 small lesions (69%) of undifferentiated type early gastric cancer were in the M region, six minute lesions (74%) and 26 small lesions (100%) were type Ⅱc, and one minute lesion (13%) and 12 small lesions (46%) were associated with peptic ulcers or ulcer scars. 3) Endoscopically, minute undifferentiated type early gastric cancer was detected as a discolored depressed lesion with very small reddish granules and an unclear margin. On the other hand, small undifferentiated type early gastric cancer was recognized as a discolored depressed lesion with reddish granules and a clear margin.

　Conclusion : It is important to look for discolored depressed lesions with reddish granules in the M region, so as not to overlook minute and small undifferentiated type early gastric cancer.