EUSが診断の契機となった潰瘍性大腸炎関連大腸癌の1例

Detection of Ulcerative Colitis-associated Rectal Cancer with Endoscopic Ultrasound

要旨●EUSが診断の契機となった潰瘍性大腸炎（UC）関連大腸癌の症例を提示した．患者は30歳代，男性で，発症後19年を経過した全大腸炎型の再燃寛解型UCである．定期検査で実施したS状結腸の内視鏡検査で近位側直腸に多発ポリープ様隆起がみられた．同時に実施したEUSで最口側の隆起直下および周囲の粘膜下層に明瞭な低エコー領域が観察された．同部位からの生検で低分化腺癌と印環細胞癌の集塊が証明された．精査後，結腸亜全摘術が施行された．切除標本肉眼所見で近位側直腸の隆起周囲には径約15mmの陥凹がみられ，病理組織学的には低分化腺癌，粘液癌，印環細胞癌から成り，粘膜下層最深部に及ぶ浸潤を示すとともに漿膜下層にも非連続的に癌巣がみられた．肛門側の隆起は高分化腺癌で粘膜に限局していた．これら2病変の周囲には平坦なdysplasiaが分布していた．郭清したリンパ節に転移はみられなかった．本症例からEUSがUC関連浸潤大腸癌を検出する上で有用である可能性があると考えられる．

　We report a case of rectal cancer associated with UC（ulcerative colitis）detected by EUS（endoscopic ultrasound）. The patient was a man in his 30s with a 19-year history of relapsing-remitting type UC affecting the entire colon. Sigmoidoscopy was performed to evaluate the disease activity and revealed multiple polypoid lesions in the proximal portion of the rectum. At the same time, EUS revealed a distinct hypoechoic area in the submucosa beneath and around the polypoid lesion on the most oral side. A cluster of poorly differentiated adenocarcinoma and signet ring cells were observed in the biopsy specimen taken from the lesion. After careful evaluation, a subtotal colectomy was performed. On inspection of the resected specimen, a depressed lesion approximately 15mm in diameter was observed around the prominence in the proximal portion of the rectum. Histologically, the lesion was a poorly differentiated, mucinous, and signet ring cell carcinoma invading the deepest portion of the submucosa with a skipped cluster of cancer cells in the subserosa. Histological examination of the polypoid lesion on the anal side revealed a well-differentiated adenocarcinoma that was limited to the mucosa. The two cancers were surrounded by flat dysplasia and there were no metastases in the dissected lymph nodes. These findings prove that EUS may be helpful for detecting invasive cancer associated with UC.