直腸リンパ濾胞性ポリープの1例

Rectal Lymphoid Polyp, Report of a Case

要旨　排便時下血を繰り返した64歳女性の直腸に発生した巨大リンパ濾胞性ポリープの1例を報告した．腫瘍はP～Rb（7～11時）に存在し，45×40mm大で山田Ⅱ型，弾性硬で表面はやや不整であった．中心にびらん形成あり，易出血性で肉眼的には悪性を強く疑った．術前の生検で，初回は悪性リンパ腫の疑い，2回目はreactive lymphoid hyperplasiaと報告を得，術前より良・悪性の鑑別が問題となった．外科的に経肛門的腫瘍切除術を行い，組織学的に直腸粘膜下層より固有筋層にかけてリンパ濾胞を一部有するリンパ球系細胞の増生がみられ最終的にlymphoid hyperplasiaと診断された．術後33か月経った現在，再発なく経過良好である．

　A rectal lymphoid polyp is one of very rare and benign non-epithelial tumors, commonly proliferating in the submucosa. It usually is present as a sessile or pedunculated polyp covered with rectal mucosa or anal skin and often eludes clinical diagnosis.

　A 64 year-old woman was admitted to our hospital complaining of bloody stool in July 1986. Digital examination revealed a tumor measuring 45 mm by 40 mm on the lateral wall of the rectum. The tumor was covered with obviously normal rectal mucosa by endoscopy. A polypoid lesion was fragile with erosive and hemorrhagic spots (Fig. 1). Barium enema double contrast picture taken in the oblique supine position revealed a filling defect about 45×40 mm at the Rb area (Fig. 2).

　Transanal local resection was carried out in September 1986.

　Examination of the resected specimen showed a sessile tumor measuring 35 mm by 30 mm by 15 mm with the cross section of the tumor being grayish white in color (Fig. 4). Histologically, the tumor was mainly located in the submucosal layer with partial invasion into the propria muscle. The tumor was composed of lyphoid tissue with follicles in the center. Each follicle, bounded obscurely, had a reaction center composed mainly of mature and juvenile lymphocytes, and plasma cells. All these findings led to the final diagnosis, reactive lymphoid hyperplasia. The patient is very well 33 months postoperatively with uneventful course.