過誤腫性病変―内視鏡診断の立場から

Hamartomatous Polyp

要旨　非腫瘍性病変である過誤腫は比較的まれな疾患であり，その病態については不明な点が多く，病変の診断に際し鑑別に苦慮する症例も存在する．若年性ポリープは直腸およびS状結腸に好発し，有茎性の強い発赤調で，びらんを伴い，上皮は剝離することが多い．表面構造は，開大した類円形，管状，星芒状など多彩なpit patternが疎に観察される．鑑別疾患として炎症性筋腺管ポリープがあるが，臨床症状や内視鏡所見も若年性ポリープと類似しており，鑑別が困難である．Peutz-Jeghers型ポリープはS状結腸に好発し，有茎性または亜有茎性の発赤調から白色調を呈する．表面構造は，類円形，管状，星芒状など多彩なpit patternが観察され，散在性に小型の蕾状や脳回状のやや腺開口部が開大したpitが認められた．鑑別疾患として，腺腫は通常観察および拡大観察においても類似した所見を呈することが多い．hamartomatous inverted polypは横行結腸から肛門側に存在し，正常粘膜で覆われた隆起性病変で有茎性または粘膜下腫瘍様形態を示す．拡大観察では軽度開大したI型の均一なpit patternが観察される．鑑別疾患として，粘膜下腫瘍様形態を示す病変やcolonic muco-submucosal elongated polypが挙げられる．自験例での検討を含め臨床像や内視鏡所見について概説したが，過誤腫は多彩な内視鏡像を呈することを認識しておく必要がある．

　Hamartomatous polyps are comparatively rare non-tumorous lesions, and much about their pathology remains unknown. Differential diagnosis for these lesions is often difficult. Juvenile polyps occur most commonly in the rectum and sigmoid colon, and in many cases are pedunculated and bright red, with erosive detachment of the epithelium. The surface structure displays a wide range of sparse pit patterns, including open round, tubular, and asteroid pits. These lesions must be distinguished from inflammatory myoglandular polyps, but as the latter present with clinical symptoms and endoscopic findings resembling those of juvenile polyps, with the exception of the fact that they are not seen in children, differentiation is difficult. Peutz-Jeghers type polyps commonly occur in the sigmoid colon, and are red or white with a pedunculated or semi-pedunculated appearance. The surface structure displays a wide variety of pit patterns, including round, tubular, and asteroid patterns, with scattered small bud-like or gyrus-like pits with somewhat dilated glandular openings. These must be distinguished from adenomas, which frequently display a similar appearance under regular and magnified observation. Hamartomatous inverted polyps occur distal to the transverse colon, and are elevated lesions covered in normal mucosa that exhibit a pedunculated or submucosal tumor-like morphology. Under magnification they display a uniform, slightly dilated type I pit pattern. These must be differentiated from colonic muco-submucosal elongated polyps or legions, which exhibit a submucosal tumor- like morphology. We have reviewed the clinical profiles and endoscopic findings of hamartomatous polyps, including an investigation of cases we have treated ourselves, and practitioners must be aware that hamartomas may display a wide range of endoscopic appearances.