片岡 咲¹, 金森 明², 橋ノ口 信一¹, 乙部 克彦¹, 今吉 由美¹, 丹羽 文彦¹, 竹島 賢治¹, 豊田 秀徳², 下山 芳江³, 熊田 卓⁴

Saki KATAOKA¹, Akira KANAMORI², Shinichi HASHINOKUCHI¹, Katsuhiko OTOBE¹, Yumi IMAYOSHI¹, Fumihiko NIWA¹, Kenji TAKESHIMA¹, Hidenori TOYODA², Yoshie SHIMOYAMA³, Takashi KUMADA⁴

¹大垣市民病院診療検査科, ²大垣市民病院消化器内科, ³名古屋大学医学部附属病院病理部, ⁴岐阜協立大学看護学部

¹Department of Clinical Examination, Ogaki Municipal Hospital, ²Department of Gastroenterology, Ogaki Municipal Hospital, ³Department of Pathology, Nagoya University Graduate School of Medicine, ⁴Department of Nursing, Gifu Kyoritsu University

キーワード : intraductal papillary neoplasm of the bile duct (IPNB), peribiliary glands, gastric type, cystic lesion

症例は78歳男性．C型肝炎ウイルス排除後で半年おきに腹部超音波検査（ultrasonography: US）による肝癌サーベイランスが行われていた．2015年1月のUSで肝左葉内側区域（S4）に径15 mmの嚢胞性病変の出現を認め，以後定期的に経過観察したところ，2016年9月に嚢胞性病変内に8 mmの結節性病変が認められたため精査となった．造影USでは動脈優位相で結節性病変が染影された．造影computed tomography（CT）およびmagnetic resonance cholangiopancreatography（MRCP）では結節性病変が小さく詳細な評価は困難であったが，内視鏡的逆行性胆管造影（Endoscopic retrograde cholangiography: ERC）ではB4胆管が造影されず，B2＋3胆管で施行した管腔内超音波検査（intraductal ultrasonography: IDUS）ではB4分岐近傍に内部が高輝度エコーを呈する腫瘤が認められた．造影US，ERC所見より胆管内乳頭状腫瘍（intraductal papillary neoplasm of bile duct: IPNB）を疑い肝拡大左葉，尾状葉切除を施行した．切除標本の肉眼所見では乳頭状結節を有する多房性病変を認め，病理組織所見では，間質浸潤のない乳頭状腺癌で既存胆管との交通が観察され，細胞形態は胃窩上皮と同様であった．以上より胃型のIPNBと診断した．本症例は経過観察のUSにより肝の嚢胞性病変と結節性病変を迅速に発見することができ，早期診断・根治治療に寄与した症例と考えられた．さらに造影USを行うことで微細な病変の血流評価が可能であり診断に有用であると考えられた．

A cystic nodule, 15 mm in diameter, was detected by ultrasonography (US) in the S4 segment of the left hepatic lobe in a 78-year-old male who achieved eradication of hepatitis C virus and was undergoing regular US surveillance every 6 months. A solid nodule, 8 mm in diameter, was found in this cystic nodule 20 months after detection of the cystic nodule and was subjected to further evaluation. A solid part was enhanced in the arterial phase of contrast-enhanced US (CEUS), whereas the imaging evaluation of this solid nodule was difficult by computed tomography or magnetic resonance cholangiopancreatography due to its minute size. The B4 bile duct was not depicted by endoscopic retrograde cholangiography (ERC), but intraductal US (IDUS) from the B2+3 bile duct depicted a hyperechoic nodule at the proximal site of the B4 branch. CEUS and ERC findings of this nodule suggested intraductal papillary neoplasm of the bile duct (IPNB), and the left hepatic lobe and the caudate lobe were resected surgically. Macroscopic examination of the resected specimen revealed a multilocular lesion including a papillary nodule, and the pathologic diagnosis was papillary adenocarcinoma without interstitial infiltration. The morphology of tumor cells was similar to that of gastric epithelium, and therefore we diagnosed this nodule as gastric IPNB. This case showed that US surveillance was useful for the detection of cystic and solid nodules in an early stage. Moreover, CEUS provided useful findings for an accurate diagnosis of IPNB.