大腸拡大内視鏡診断における腫瘍・非腫瘍の鑑別

Differential Diagnosis of Neoplastic/Non-neoplastic Colorectal Tumors by Using Magnifying Endoscopy

要旨　大腸における内視鏡診断の要素として，病変の腺管開口部の形態から診断する拡大内視鏡診断，pit pattern診断は既に市民権を得ていると思われる．今回上皮性由来の病変に関する腫瘍・非腫瘍の鑑別について検討を行った．当センターにおいて拡大内視鏡観察が行われ，かつ標本が切除され病理組織学的検討を行った隆起型・表面型1,328病変を対象として，I・II型pit patternを呈する非腫瘍性pit群とIII～V型pit patternを呈する腫瘍性pit群の2群に大別して，その病理組織像と対比した．また誤診例についても検討した．その結果，拡大内視鏡による腫瘍・非腫瘍の鑑別は感度，特異度が89.3％，96.2％（p＜0.01）と高値を示し十分に信頼に足るものであったが，今回の検討はretrospective studyであるためバイアスが含まれており，これを是正するとさらなる高い診断能であることが示唆された．一方誤診した病変の検討では，非腫瘍性pitと判断した群では低異型度腺腫，5mm以下の微小病変が多く，また腫瘍性pitと判断した病変群では炎症性ポリープ，過形成性ポリープと誤診される場合が指摘でき，これらの病変を診断する際は注意を要すると思われた．

　Recently, we can use magnifying endoscopy for endoscopic diagnosis of colorectal tumors. It is called “pit pattern diagnosis” when we diagnose pathological features from the magnified surface structure of colorectal tumors. In this article, in retrospective study, we investigatable ability of pit pattern diagnosis for differential diagnosis of neoplastic/non-neoplastic colorectal tumors. The subjects were 1,328 cases in which we could observe surface structure by using magnifying endoscopy, and which were taken from specimens after endoscopic or surgical resection in our hospital. We defined type I and II pit pattern as non-neoplastic, type III, IV and V pit pattern as neoplastic surface structure, and we calculated our accuracy through comparison with pathological diagnoses. The results showed a high rate of accuracy, with sensitivity ; 89.3％, and specificity ; 96.2％ (p＜0.01). On the other hand we made a wrong diagnosis in a few cases, for example ; we diagnosed low grade adenomas and lesions under 5 mm in size as non-neoplastic pit pattern, and inflammatory polyps and hyperplastic polyps as neoplastic ones. In conclusion, we proved that it is possible to make differential diagnosis of neoplastic/non-neoplastic colorectal tumors by using magnifying endoscopy. If we can carry out a prospective study about this same theme, that we will be able to achieve an even higher accuracy rate.