咽頭・食道癌の拡大観察に必要な基本的病理知識

Basic Histopathological Knowledge Required to Perform Magnifying Endoscopy in Patients with Pharyngeal and Esophageal Cancers

要旨●咽頭・食道領域の拡大内視鏡診断に際して理解しておくことが望ましい病理学的事項をまとめた．上皮内扁平上皮癌の最表層部では乳頭内毛細血管の変化が主たる役割を担っており，上皮下毛細血管の変化は軽度であるが，進展に伴う表層部の脱落が進むと乳頭が消失して上皮下毛細血管を基盤とした血管が表層から視認されるようになる．粘膜下層深部浸潤癌の間質増生に伴い出現する血管は，細径のものから太径のものまでさまざまである．表面（上皮内癌成分）の脱落の程度と壁深達度には相関があるが，表層が保たれたまま深部浸潤を示す病変や，壁深達度の浅い病変でもびらん，炎症により表層の脱落が目立つ病変もあり，その場合には拡大内視鏡所見と壁深達度に乖離が生じる．Barrett食道腺癌における内視鏡診断困難例は，①背景粘膜の要素，すなわち背景円柱上皮粘膜において表面構造不整がみられること，②腫瘍側の要素，すなわち低異型度腫瘍の存在と非腫瘍成分の被覆の複合によると考えられる．

　Herein we describe the histopathological knowledge necessary for use of magnifying endoscopy in the pharynx and esophagus. In squamous cell carcinoma in situ, alteration of capillary vessels in the papilla plays a major role, whereas there are minimal changes of subepithelial capillary vessels. However, with deeper invasion, exfoliation of the intraepithelial component due to erosion and degeneration can obscure observation of capillary vessels in the papilla. Alternatively, irregularly-shaped vessels derived from subepithelial capillary vessels may appear on the surface of the tumor. Tumors with deeper submucosal invasion may exhibit surface desmoplasia（including fibroblastic and vascular proliferation）. In these tumors, surface vessels of various diameters are often observed. In patients with Barrett's esophagus, endoscopic diagnosis difficulties may be due to irregularities of background columnar-lined mucosa, higher frequency of adenocarcinoma with low-grade architectural atypia, and tumor components covered with non-neoplastic epithelium.