非定型的炎症性腸疾患の病理学的鑑別診断―肉芽腫の鑑別を中心に

Pathological Differential Diagnosis of Indeterminate Colitis: Discrimination of the Granulomatous Lesion

要旨　炎症性腸疾患（IBD）の中で潰瘍性大腸炎（UC）とCrohn病（CD）の鑑別が困難な症例はindeterminate colitis（IC）として扱われることが多い．CDの病理組織診断においては類上皮細胞肉芽腫が特異度も高く最も重要な所見とされる．しかしUCでも陰窩に関連する肉芽腫性病変を認めることがありその鑑別が必要となる．われわれのUC手術例の検討では，20例中15例（75％）に陰窩関連の肉芽腫性病変が粘膜固有層に認められ，CDの類上皮細胞肉芽腫との鑑別に難渋する病変もみられた．一方UCあるいはICの臨床診断で類上皮細胞肉芽腫が検出されCDと確定診断された10例の検討では，初回診断時のX線・内視鏡像は全例でUC様の腸炎像が全結腸あるいは左側結腸にみられたが，生検の組織像は巣状の炎症細胞浸潤像を呈するものが多く，手術材料ではリンパ球集簇を主とする全層性炎症と類上皮細胞肉芽腫が確認された．CDとUCの組織診断を行う際には，類上皮細胞肉芽腫の検出およびそれと陰窩関連肉芽腫性病変の鑑別が最も大切であるということを念頭に入れながら，臨床所見，X線・内視鏡像等を加味した総合的診断を行うことが肝要であると結論した．

　Indeterminate colitis (IC) is used for inflammatory bowel disease (IBD) cases in which a definite diagnosis of ulcerative colitis (UC) or Crohn's disease (CD) cannot be established. Diacrisis of granuloma is important when making pathological diagnosis of CD. However, a granulomatous lesion (crypt associated granuloma) is seen in ulcerative colitis, and diacrisis with CD is necessary. The present study investigates characteristic pathologic findings of the granulomatous lesion in patients with resected UC, and its difference from an epithelioid cell granuloma in CD. Furthermore, examination of ten cases of IC or UC in the initial clinical diagnosis was made after the pathological diagnosis of CD in findings of epithelioid cell granuloma. The rate of granulomatous lesions in resected UC was 75％ (15/20). All the crypt associated granulomatous lesions in UC were detected only in the muscularis mucosa, and some revealed lesions in which diacrisis from a granuloma of CD was difficult. The characteristic of ten cases in patients with CD that initially received clinical diagnosis as UC or IC shows UC-like colitis in radiologic and endoscopic findings. The granuloma of these cases was detected in the lamina propria, submucosa and muscularis propria. Pathological diagnosis of IBD is not always easy, and should be generally diagnosed with clinical observation, treatment course, radiologic and endoscopic findings, and a pathological diagnosis of IC should not be made lightly.