本文報告一位82 歲男性病人在實施經肛門直腸基質細胞瘤切片後，引發預期外嚴重出血的併發症。病人至本院主訴間歇性血便有一個多月，大腸鏡檢查發現直腸有一巨大的黏膜下腫瘤，黏膜表面有散在性的潰瘍，於是實施經肛門腫瘤切片，來做診斷。手術中發現大量鮮血及部分腫瘤從肛門直腸交接處之小切口冒出，術後因持續出血導致生命現象不穩定，於是在6 小時後緊急實施腹部會陰聯合切除術。病理切片結果顯示此腫瘤為直腸基質細胞瘤，病人術後2 週因感染肺炎而過世。本病例顯示一個簡單的經肛門直腸基質細胞瘤切片手術也可能引起無法控制的出血。基於可能潛藏的出血危機，若一個直腸黏膜下的腫瘤大到它的上緣是經肛門手術時無法接近得到的，那麼就不建議做經肛門的切片，比較好的方法應該是仔細評估後，在好的視野下做一完整的腫瘤切除手術。

Unexpected massive bleeding following a transanal incisional biopsy for a rectalgastrointestinal stromal tumor in an 82-year-old man is reported. This patient presented to thehospital with a 1-month history of intermittent bloody stool. A colonoscope was inserted to thececum and disclosed a huge submucosal tumor of the rectum with several scattered mucosal ulcers.A transanal incisional biopsy was performed to determine the diagnosis of this unknown mass.Serious hemorrhage with gushing out of part of the tumor through the small incisional wound overthe anorectal junction occurred. A salvage abdominal perineal resectionwas performed 6 hours afterthe initial surgery due to continued bleeding which caused an unstable hemodynamic condition.Microscopically the tumor was revealed to be a gastrointestinal stromal tumor. The patient died ofpneumonia 2 weeks later. The case presented shows that uncontrollable bleeding is possible after atransanal incisional biopsy for a huge rectal gastrointestinal stromal tumor. Based on this latentcomplication, a transanal incisional biopsy formaking a tissue diagnosis is not recommended becausethe upper border of an extrarectal mass is not accessible during the procedure. Total gross excisionof the tumor after a complete preoperative study is the treatment of choice.