内視鏡的完全一括切除可能な大腸T1癌の術前診断—拡大内視鏡の有用性と限界

Usefulness and Limitations of the Magnifying Endoscopic Diagnosis for Colorectal Lesions

要旨●JNET分類Type 1，2A，3と高確信度で診断された大腸病変は，色素拡大内視鏡診断（pit pattern診断）を省略して治療方針決定が可能である．一方，JNET分類Type 2Bと診断された病変，あるいはJNET分類Type 1，2A，3でも低確信度で診断された場合にはpit pattern診断の追加が必要である．JNET分類Type 2BかつIII_S/III_L/IV/V_I型軽度不整pit patternと診断された病変は内視鏡切除の適応であるが，JNET分類Type 2BかつV_I型高度不整pit patternと診断された病変は約半数がT1b癌であり，EUSや注腸X線造影検査を追加して治療方針を決定すべきである．また，JNET分類Type 2Bを不整度によってType 2B-lowとType 2B-highに細分類した場合，Type 2B-lowは腺腫〜T1a癌までの病変であり，内視鏡切除の適応になる．Type 2B-lowと診断した病変はpit pattern診断を省略できる可能性がある．

　JNET（the Japan NBI Expert Team）classification consists of four categories（Types 1, 2A, 2B, and 3）. Types 1, 2A, and 3 are reliable indicators, with high diagnostic accuracy for hyperplastic polyp/sessile serrated polyp, low-grade intramucosal dysplasia, and deep submucosal invasive carcinoma, respectively. There is no need to enhance a diagnostic pattern for these lesions using dyes. Otherwise, the diagnostic ability of Type 2B for high-grade intramucosal dysplasia/superficial submucosal invasive carcinoma is insufficient. A pit pattern diagnosis should be made to define a more precise Type 2B lesion or in low-confidence categories. Type 2B and III_S/III_L/IV/V_I mild pit pattern lesions are a good indication for endoscopic resection. However, about half of the Type 2B and III_S/III_L/IV/V_I severe pit pattern lesions are deep submucosal invasive carcinomas. Therefore, additional assessments, such as endoscopic ultrasound or barium enema X-ray examination, are necessary for an accurate diagnosis of Type 2B and III_S/III_L/IV/V_I severe pit pattern lesions. We divided JNET Type 2B into Type 2B-low and Type 2B-high lesions. JNET Type 2B-low lesion is a good indication for endoscopic resection ; therefore, an additional pit pattern diagnosis may not be necessary. Whereas, JNET Type 2B-high lesion includes several histopathologies ; thus, an additional pit pattern diagnosis is necessary.