膿瘍形成性虫垂炎との鑑別に苦慮した原発性虫垂癌の3例

Three cases of primary appendiceal carcinoma that initially misdiagnosed as abscess-forming appendicitis on CT imaging

膿瘍形成を伴う虫垂炎は従来，緊急手術の適応とされていたが，近年では保存的治療後に待機的虫垂切除術（interval appendectomy：IA）を行う報告が増えており，術後合併症や拡大手術の回避，腹腔鏡手術実施の観点から有用であることが報告されている^1）2）。一方，原発性虫垂癌は術前の画像診断で虫垂炎や回盲部膿瘍とされることが多く，早期診断が困難なことで知られており^3），原発性虫垂癌と膿瘍形成性虫垂炎の鑑別は重要である。今回，初診時に膿瘍形成性虫垂炎と診断しIAの方針としたが，結果的に虫垂粘液性腫瘍であった3症例を経験したので，画像診断の観点からこれらを報告する。

Primary appendiceal carcinoma is often difficult to diagnose early and is frequently misdiagnosed as appendicitis preoperatively. We reported three cases initially misdiagnosed as abscess-forming appendicitis because abscess size reduction on short-interval follow-up CT, however which were final pathological diagnosis revealed primary appendiceal carcinoma. Three CT findings were important to identified to differentiate primary appendiceal carcinoma from abscess-forming appendicitis：① subtle contrast enhancement within the fluid collection, ② calcifications different from typical appendicoliths, and ③ presence of peritoneal dissemination and lymph node metastases.