食道表在癌の深達度診断を誤った要因―内視鏡の立場から

Why is it Difficult to Diagnose the Invasion Depth of Superficial Esophageal Cancer?

要旨　食道表在癌の深達度を誤らせる要因として①観察困難部位の存在，②リンパ濾胞の影響，③微小浸潤，④浸潤部を粘膜癌が被う，⑤Infγの浸潤性発育，⑥病理診断基準の問題，が挙げられた．本稿ではこれらの具体的例を挙げ，現時点での内視鏡的深達度診断の限界を提示した．今後さらに症例を重ね，診断精度を向上させるためには術前の画像と切り出し標本との一対一対応が必須であり，そのためには一括切除が必要である．

　Recently, although the incidence of superficial esophageal cancer has increased and the quality of esophagoscopy has become better, we still sometimes misjudge the invasion depth. What is the cause of this difficulty in diagnosing invasion depth.

　When the lymph follicles of the proper mucosal layer push up the lesion, the lesion reveals marked protrusion, so the endoscopist might think the cancer has invaded the submucosal layer. But in much cases, the shape of the lesion also changes. This is because the lymph follicles are soft. Observation of the shape change is thus very important (Fig. 1-4).

　When the area of invasion is about one or two mm, the diagnosis of submucosal invasion is difficult (Fig. 5-9).

　When a submucosal invading cancer is exposed to the surface, the surface pattern becomes irregular. But if the cancer is covered by a mucosal cancer, the surface of the submucosal invaded part appears smooth, so the diagnosis of invasion depth might be very difficult in these cases (Fig. 10).

　When the cancer has invaded the submucosal layer with an infiltrative growth pattern, the diagnosis of submucosal invasion is difficult especially in the early stage of invasion (Fig. 11, 12).

　Sometime shallow muscle bundles continuous form muscularis mucosa rose up to the proper mucosal layer and contacted with the mucosal cancer (Fig. 13). The invasion depth is diagnosed as m3in these cases, but the cancer limited within the proper mucosal layer. So, the new criteria should be established to distinguish the true invasive m3from such as false invasion.

　1) Department of Gastroenterology, Saku Central Hospital, Nagano, Japan