EUSで浸潤部の読影が困難であった大腸鋸歯状腺腫由来のsm2浸潤癌の1例

Cancer with sm2 Invasion Complicating a Serrated Adenoma in which the Visualization of sm Invasion by EUS was Difficult, Report of a Case

要旨　患者は便潜血陽性精査のために大腸内視鏡を行った41歳，男性で，S状結腸に有茎性および亜有茎性の2個のポリープが近接して認められた．いずれも絨毛状の表面性状を有し大きさは10mmくらいであったが，亜有茎性病変では表面に不明瞭な陥凹を伴い周辺部に小結節状の隆起がみられsm浸潤癌が疑われた．確認のために細径超音波プローブで観察したところ，第3層内にのびる比較的低エコーの領域が認められたものの良好な描出は得られなかった．結局，局注で病変の十分な挙上がみられたためtotal biopsyの目的でEMRを施行した．組織は有茎性病変が鋸歯状腺腫であり，亜有茎性病変は鋸歯状腺腫由来のsm2浸潤癌であり高度の間質反応を伴う中分化腺癌の浸潤がみられた．本例ではEUSが効果的であったとは言えないが，1つの描出パターンとして認識すればEUSの診断能を更に向上することができると考えられる．

　We reported a case of a 41-year-old male in which two polypoid lesions were found in the sigmoid colon by close examination for positive fecal occult blood. Colonoscopy revealed that a pedunculated polyp and a semipedunculated one existed in close proximity. Both lesions had villous surface and both were about 10 mm in diameter. The semipedunculated lesion was accompanied by an indistinct depression on the top and nodular protrusions on the periphery. Accordingly, cancer with massive submucosal invasion was suspected by ordinary colonoscopy. However, EUS with a miniature ultrasonic probe was conducted to confirm the diagnosis. EUS revealed a hypoechoic area extending into the third layer, but, the quality of the images were not satisfactory. Although cancer with massive submucosal invasion was suspected, the lesions were completely elevated by injection of glucose solution. Consequently, EMR was performed for total biopsy. Histologically, the pedunculated polyp was a serrated adenoma. The semipedunculated one was cancer with sm2 invasion complicating the serrated adenoma. Invasion of the moderately differentiated adenocarcinoma with marked interstitial reaction was observed. In this case, EUS proved to be not so effective. However, it was considered important to recognize such a pattern as was observed in this case as a reference to improve the diagnostic ability of EUS.