内視鏡的ポリペクトミーの6年後に肺転移を来したIp型大腸sm癌の1例

Ip-type Submucosal Invasive Colonic Cancer with Lung Metastasis 6 years after Endoscopic Polypectomy, Report of a Case

要旨　患者は49歳，女性．便潜血反応陽性．下行結腸に頭部が約10mm大で不整なIp型の隆起性病変を認め，内視鏡的ポリペクトミーを施行した．組織学的に腺腫成分を伴う高分化型腺癌で，ポリープの頭部と茎部の境界までsm浸潤していたが，脈管侵襲は陰性で切除断端も十分であった．その後，経過観察していたが，6年後に内視鏡的endobronchial metastasisを伴う肺転移で再発した．ポリペクトミー標本の再検索にて，癌先進部に簇出像が確認された．内視鏡治療後は，たとえIp型病変であっても，浸潤部の組織学的所見に注意し，慎重かつ長期的な経過観察が重要と考えられた．

　A 49-year-old woman tested positive for fecal occult blood. Colonscopy revealed a Ip-type irregular surfaced protruding lesion, measuring 10mm, in the descending colon. We performed endoscopic polypectomy for this lesion. Histologically, the lesion showed adenoma and well differentiated adenocarcinoma, invading to the level of the junction between the adenoma and its stalk, without lymphatic or venous permeation. However 6 years after endoscopic polypectomy, an examination of chest CT and bronchoscopy showed lung metastasis with endobronchial invasion. We reviewed the colonic resected specimen histologically, and detected a sprouting of cancer cells at the invasive front. It was concluded that histological findings at the invasive front and long-term follow-up are very important for colonic submucosal cancers, even for those such as this Ip-type, after endoscopic polypectomy.