5mm以下の大腸微小腺腫の診断と治療方針―肉眼型とpit patternの解析から

Diagnosis and Therapeutic Guideline for Minute (Less than 5 mm) Colorectal Adenomas: From the Viewpoint of Its Macroscopic Appearance and Pit Pattern

要旨　内視鏡的に切除された5mm以下の大腸腫瘍性病変の組織型，肉眼型pit patternを解析し，5mm以下の腺腫の診断と治療方針について検討した．5mm以下の腺腫の形状は隆起型(Is・Isp)が最も多く72％を呈し，陥凹型(IIc・IIc＋IIa)を呈するものはわずか4.2％であった．また，pit patternの解析では，隆起型や表面隆起型(IIa)病変ではIII_L型pitを呈するものが約75～90％を占め，陥凹型病変ではIIIs pitを呈するものが約70％を占めた．また，III_L pitを呈する病変は腺腫が80％を占め，IIIs pitを呈するものでは癌が67％を占めた．このことから，隆起型や表面隆起型でIII_L pitを呈する病変はほとんど腺腫であり，直ちに内視鏡治療を行う必要性がないと考えられた．一方，陥凹型でIIIs pitを呈するものは癌の可能性が高く慎重な治療方針が必要と考えられた．拡大内視鏡と実体顕微鏡の比較では，他の型のpitに比してIIIs型の一致率がやや悪く正確な臨床診断を得るためには工夫が必要と考えられた．

　Endoscopically resected minute (less than 5 mm) colorectal adenomas are analyzed for their histology, macroscopic appearances and pit patterns, and their diagnosis and therapy are evaluated on the basis of the analysis. Ninety six percent of them were exophytic in type (Ip, Is, Isp, IIa). In contrast, only 4.2% of them were depressed type (IIc, IIc+IIa).

　In terms of pit pattern, about 90% of the exophytic neoplasms showed III_L. type (long tubular pit) and 70% of the depressed type neoplasms showed IIIs type (small round pit). Eighty percent of neoplasms with III_L pits were adenoma, and 67% of neoplasms with IIIs pits were carcinoma. The diagnosis of pit pattern (I, II, III_L, IV, V) using magnification endoscopy mostly (about 90%) correspond to pit pattern findings of stereomicroscopy except for IIIs pit.

　These results suggest that exophytic lesions with III_L. pits are mostly adenoma and able to be followed up without endoscopic resection. This is in contrast to depressed lesions with IIIs pits. Moreover, magnification endoscopy was shown to be useful for pit pattern diagnosis and for the decision of therapeutic guideline of minute colorectal neoplasms.