福田 順子¹, 田中 幸子¹, 仲尾 美穂¹, 上田 絵理¹, 鈴木 玲子¹, 高倉 玲奈¹, 高野 保名¹, 井岡 達也¹, 吉岡 二三¹, 冨田 裕彦²

Junko FUKUDA¹, Sachiko TANAKA¹, Miho NAKAO¹, Eri UEDA¹, Reiko SUZUKI¹, Rena TAKAKURA¹, Yasuna TAKANO¹, Tatsuya IOKA¹, Fumi YOSHIOKA¹, Yasuhiko TOMITA²

¹地方独立行政法人大阪府立病院機構大阪府立成人病センター検診部, ²地方独立行政法人大阪府立病院機構大阪府立成人病センター病理・細胞診断科

¹Department of Cancer Survey, Osaka Medical Center for Cancer, ²Department of Pathology, Osaka Medical Center for Cancer

キーワード : ultrasonography, three-dimensional ultrasonography, pancreatic mucinous cystic neoplasm, contrast ultrasonography

膵粘液性嚢胞腫瘍（MCN）は比較的稀な疾患であり，長期にわたり経過観察された報告は少ない．今回5年間の経過中，画像上多彩な変化を認め，自然経過を知る上で興味深い症例を経験した．また，診断には超音波検査（US）時のボリュームデータから作製したvirtual sonographic cystoscopyが有用であった．症例は50歳代女性．既往歴に特記事項なし．左側腹部痛を訴えて受診し，初診時のUSで膵体尾部に24mm大の単房性嚢胞を指摘された．MRCPでは嚢胞の尾側の膵管拡張を認め，ERPでは嚢胞は造影され主膵管との交通が明らかとなった．上流側の主膵管は造影されず，小膵癌によるretention cystやIPMCを疑ったが，膵液細胞診は陰性であった．経過中の嚢胞径は概ね15-20mm大であったが，腹痛を伴う一過性の嚢胞径増大（26mm大）を認め，膵炎による仮性嚢胞の可能性も示唆された．5年後のUSでは隔壁を疑い，Sonazoid^®造影3DUSでcyst in cystが明瞭に描出されMCNを疑った．3ヵ月後に嚢胞径は30mm大に増大，より細かいcyst in cystが描出された．また，virtual sonographic cystoscopyでは平滑な球状の内腔面とcyst in cystを立体画像で表示でき，画像上MCNと診断した．切除手術の結果，病理組織学的にMCNと確定診断された．本例は当初，主膵管と交通する単房性嚢胞として発見され，長期間の経過中に嚢胞径の増大やcyst in cystの出現という多彩な変化を来し，臨床的に診断の難しい症例であったが，最終的にはUSで画像上典型的なMCNの像を呈し，診断に有用であった．

Pancreatic mucinous cystic neoplasms have a potential for malignancy, and surgical resection is usually recommended. Therefore, long-term follow-up of this disease is rarely reported. We experienced a case of mucinous cystic neoplasm in which the appearance and size of the cyst changed markedly during five years of follow-up. A simple cyst of 24 mm in diameter was detected occupying the body to the tail of the pancreas of a woman in her 50s who complained of left upper abdominal pain. The communication between the cyst and the main pancreatic duct was revealed with endoscopic retrograde pancreatography, and the main pancreatic duct dilatation at the upper stream of the cyst was detected by magnetic resonance pancreatography. The cyst was initially suspected to be an intra-ductal papillary mucinous neoplasm. Pancreatic juice cytology was negative, so the cyst was followed-up with ultrasonography every three month. During the follow-up period, the size of the cyst remained around 15 to 20 mm, but transient enlargement was observed accompanied with symptoms of acute pancreatitis. So that it was also suspected to be a pseudo cyst caused by pancreatitis. Five years later, a septum was first detected in the cyst, and after that pleural septa appeared. On contrast-enhanced ultrasonography, the septa within the cyst were strongly enhanced, and the so-called cyst-in-cyst appearance, a characteristic finding of a mucinous cystic neoplasm, was clearly visualized. Moreover, virtual sonographic cystoscopy reconstructed from the volume data depicted the cyst as having a smooth internal surface without any nodules. Both of these techniques were very useful for diagnosis of this case as a benign mucinous cystic neoplasm. After surgical resection, the lesion was pathologically confirmed to be a mucinous cystic neoplasm with moderate dysplasia.