胃腫瘍性病変の拡大内視鏡診断―腺腫も含む隆起型上皮性腫瘍

Magnifying Endoscopic Diagnosis for Elevated Early Gastric Cancer and Adenoma

要旨　隆起性胃腫瘍は早期胃癌では隆起型（0-I型）と表面隆起型（0-IIa型）に分類される．「胃癌取扱い規約」による肉眼型分類の違いは，第13版までは隆起の高さが正常粘膜の2倍以内のものを0-IIaとし，それを超えるものを0-Iとしてきたが，第14版では現実には隆起の高さが2～3mmまでのものを0-IIaとし，それを超えるものを0-Iとするのが一般的であるとしている．隆起性早期胃癌のNBI併用拡大内視鏡観察では，粘膜微細模様の微小・不整化があるものが比較的多く，微小血管模様においてはISIV（intrastructural irregular vessel ; 構造内不整血管）が診断の決め手となることがあった．また臨床的に胃腺腫の取り扱いが問題になることがあり，筆者らの施設による胃腺腫の検討において，大きさ2cm以上，生検で高異型度，陥凹型や発赤調の胃腺腫でESD切除標本の最終病理診断が腺癌（腺腫内癌）であったもの（“悪性度が高い腺腫”）が高率に認められた．

　Elevated early gastric cancers are classified into two categories : type 0-I protruded lesions and type 0IIa superficial elevated lesions. Type 0-I cancers are 3mm or more in height, and type 0-IIa cancers are less than 3mm. Irregularity of fine mucosal structure can be observed in elevated early gastric cancers by using ME-NBI（magnifying endoscopy combined with narrow band imaging）. In elevated early gastric cancers, as well as the marginal flat area of an elevated or depressed lesion, a specific microvascular pattern called ISIV（intrastructural irregular vessel）is observed. ISIV is a group of microvessels enclosed in round or papillary fine mucosal structure, which show irregularities such as heterogeneous shape, uneven caliber, and abnormal dilatation.

　Gastric adenoma, a benign neoplastic lesion in the stomach, is often difficult to correctly diagnose in terms of its malignant potential and how it differentiates from cancer. We defined the following lesions as adenoma with malignant potential ; gastric lesions with a pre-ESD pathological diagnosis of adenoma, those with a final pathological diagnosis of ESD specimens, those determined to be gastric cancer or a cancer in adenoma. Analyzing 192 adenomas diagnosed with pre-ESD pathology, predicting factors for‘highly-malignant adenoma'were severe atypia in biopsies, lesions larger 2cm in diameter, depressed type lesions or reddish lesions.