拡大内視鏡観察にて術前診断しえた大腸衝突腫瘍（深達度SM）の1例

Collision of Tumors in the Ascending Colon that was Diagnosed by Magnifying Endoscopy, Report of a Case

要旨　患者は57歳，男性．便潜血陽性にて近医で大腸内視鏡を行い上行結腸の病変を指摘され，2006年9月紹介受診となった．注腸X線像では，病変は大きさ約4cm弱の透亮像として描出され，丈の高い隆起と平坦部分から成り，中央にバリウム斑が観察された．12日後に内視鏡検査を行い，上行結腸に立ち上がり急峻な隆起と淡く発赤した平坦部分を認めた．隆起部分はLST-NG（flat elevated type ; F）様で，平坦部分はLST-NG（pseudo-depressed type ; PD）に相当し，両成分の境界ではI型pitの帯状粘膜が観察された．43日後の内視鏡検査では陥凹は厚みを増してVn型pitを示し，境界の正常粘膜は幅が狭く，一部で不規則不明瞭となった．11月手術を行った．切除標本では病変は37×13mmで，LST-NG（PD）様部分は18×10mm，LST-NG（F）様部分は19×13mmであった．病理組織所見では，病変は粘膜固有層深部に囊胞状に拡張した腺管を有する中等度異型腺腫の隆起部分と高度異型腺腫から成る平坦部分の異なる2つの腫瘍から構成された．これらは粘液性状からも区別され，境界部に正常腺管が残存し移行像を認めなかったことから，2つの腫瘍が衝突した衝突腫瘍と診断された．また，Vn型pitの部分では中分化腺癌の所見で，pSM3（1,050μm）, ly0, v1, pN0であった．

　This is a case report of the collision of tumors in the ascending colon. In this case, we observed a morphological change by using magnifying endoscopy. The case is 57-year-old male patient. He was pointed out as having faecal occult blood positive on examination, and underwent a colonoscopy on September,2006. He was diagnosed with a lesion of the ascending colon, and was introduced to our department. With X-ray examination, the lesion was located on a fold of the ascending colon, and it was revealed as a shadow of about 4cm in size. In addition, the lesion consisted of a slightly elevated part and a flat part, and a small barium deposit was observed in its center part.

　Colonoscopy was performed on 12 days later. The lesion consisted of a slightly elevated area and a flat part on the fold of the ascending colon. The elevated part of the lesion showed a macroscopic configuration of LST-NG（flat elevated type : F）, and the flat part was similar to LST-NG（pseudo-depressed type : PD）. Normal mucosa comprised of type I pit pattern was observed in the marginal area of the depressed part. The thickness of the depressed part had increased by the time of the second examination and showed type Vn pit pattern. In addition, the central normal mucosa showed narrowness and irregularity. From the above, we diagnosed the lesion as a submucosal massively invasive cancer, and performed right hemicolectomy on November, 2006. According to the macroscopic examination of the resected specimen, the lesion（37×13mm in size） consisted of two components. A LST-NG（PD）-like part with a size of 18×10mm and the LST-NG（F）-like part including a part with type Vn pit pattern was size of 19×13mm.

　A histological examination revealed that the lesion had two tumor components. The elevated part was consisted of a low grade adenoma, with the cystic gland in a deep part of a mucosal layer. Otherwise, the flat part was composed of a high grade adenoma. Remnant of a normal gland was seen between both, and the transitional zone was not recognized. In addition, a moderately differentiated adenocarcinoma was seen in the part of type Vn pit pattern, and its degree of cancer invasion was SM3（1,050μm）. From the above, it was concluded that this was a case of the collision of two tumors resulting in the lesion having two tumor components.