胃癌診断における生検診断の現状と問題点

The State of the Art and Problems of Endoscopic Biopsy in Diagnosis of Gastric Cancer

要旨　胃内視鏡が施行され生検が行われた症例の内視鏡像を，G1：良性にしか見えない，G2：癌（悪性）を否定しえない，G3：癌か良性かはっきりしないがおそらく腫瘍（腺腫に相当），G4：癌（悪性）を積極的に疑う，G5：癌（悪性）にしか見えない，の5段階に分類し，生検組織像との対比を行い胃癌診断における生検の役割を検討した．対象症例737例中G1が413例，G2が256例，G3が18例，G4が21例，G5が29例であった．各群での癌検出率は，G1が0.2％，G2が1.6％，G3が11.1％，G4が66.7％，G5が100％であった．また，内視鏡像と組織像の一致率は95.8％であった．内視鏡で癌と判定（G4, 5）されたが生検では良性であった症例は7例（全体の0.9％）で，逆に内視鏡で良性（G1, 2）と判定されたが生検で癖であった症例は5例（全体の0.7％）であった．現状では内視鏡的に良悪性の鑑別がかなり可能であるが，良性と判定している症例にもかなりの数の生検が施行されている．そして，肉眼的に悪性の所見が乏しい癌や悪性様所見を呈する良性病変も少なからず存在するので，確定診断においては生検が重要な役割を果たしている．

　The endoscopic appearances of cases, in which endoscopic biopsy was performed, were classified into five groups, G1; definitely benign, G2; probable benign, G3; neoplasm of borderline malignancy (adenoma), G4; suspicious of malignancy, G5; definitely malignant. Then, the correlation between the endoscopic diagnosis and histologic diagnosis was evaluated.

　Of 737 cases, 413 were classified into G1, 256 were classified into G2, 18 were classified into G3, 21 were classified into G4, and 29 were classified into G5. The incidences of malignancy in G1, 2, 3, 4 and 5 were 0.2％, 1.6％, 11.1％, 66.7％ and 100％, respectively. The endoscopic diagnosis was in good agreement with the histologic diagnosis. Its ratio of agreement was 95.8％. Of 737 cases, histology was unable to detect malignancy in only 0.9％ of G4 or G5 cases, whereas 0.7％ of G1 or G2 cases revealed malignancy.

　Malignancy could be correctly distinguished from benignancy by endoscopic appearance in almost all cases. However, biopsy was performed in most benign cases, because malignancy with benign appearance does exist, and histologic diagnosis by biopsy is considered to be essential for a final diagnosis.