Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
Int J Clin Oncol. 2010 Dec;15(6):601-7. doi: 10.1007/s10147-010-0084-3. Epub 2010 May 11.
A 54-year-old man presented with pain on defecation and rectal bleeding. Colonoscopy revealed a submucosal tumor extending from the lower rectum to the upper rim of the anal canal, which compressed the rectal wall inward by two thirds of its circumference. Magnetic resonance images demonstrated a 70 × 80-mm unilocular cystic mass with a solid portion in the periphery in the retrorectal space, which displaced the rectum anterolaterally. The peripheral solid portion was hypointense on T2-weighted images and not hyperintense on diffusion-weighted images, suggesting low cellularity of the lesion. Cytological examination of the clear and serous fluid obtained by transrectal biopsy showed the presence of normal columnar and squamous epithelial cells and the absence of malignant cells. Therefore, the cystic retrorectal mass was presumed to be tailgut cysts rather than gastrointestinal stromal tumors (GISTs). The mass and rectum were extirpated en bloc with an adequate surgical margin by laparoscopic intersphincteric resection. Pathologically, spindle tumor cells proliferated with nuclear palisading and were strongly immunopositive for c-kit, leading to a final diagnosis of rectal GIST. There are no reports describing a huge, cystic rectal GIST arising in the retrorectal space, which should be considered in the differential diagnosis of cystic retrorectal lesions.
一位 54 岁男性因排便疼痛和直肠出血就诊。结肠镜检查显示直肠下段至肛管上缘的黏膜下肿瘤，将直肠壁向内压迫三分之二周径。磁共振成像显示直肠后间隙有一个 70×80mm 的单房囊性肿块，周边有实性部分，将直肠向前外侧推移。外周实性部分在 T2 加权图像上呈低信号，在弥散加权图像上不呈高信号，提示病变细胞密度低。经直肠活检获得的透明和浆液性液体的细胞学检查显示存在正常柱状和鳞状上皮细胞，没有恶性细胞。因此，推测囊性直肠后肿块为尾肠囊肿而不是胃肠道间质瘤（GIST）。肿块和直肠通过腹腔镜经括约肌间切除术整块切除，并保证了足够的手术切缘。病理上，梭形肿瘤细胞呈核栅状增生，对 c-kit 呈强免疫阳性反应，最终诊断为直肠 GIST。目前尚无文献报道描述起源于直肠后间隙的巨大囊性直肠 GIST，在囊性直肠后病变的鉴别诊断中应考虑到这一点。
