腹腔鏡を併用し前立腺癌と一塊に局所切除した直腸GISTの1例

A case of rectal gastrointestinal stromal tumor locally resected with prostate cancer under laparoscopic and transanal approach

◆要旨：患者は64歳，男性．前立腺癌術前精査中の骨盤MRI検査にて，下部直腸左前壁に前立腺に接する14mm大の粘膜下腫瘍を指摘された．経直腸的腫瘍生検で直腸GISTの診断を得た．術野への腫瘍の露出や播種を避けるため，腹腔鏡を併用した一括切除を試みた．まず腹腔鏡下に直腸の剝離・授動を粘膜下腫瘍の存在する前壁を除いて骨盤底まで進め，経肛門操作にてGISTを前立腺側に付けるように直腸を円状・全層性に局所切除し，切除部を縫合閉鎖した．引き続き腹腔鏡下前立腺摘除術を施行した．病理組織学的検査で，両腫瘍ともに断端陰性を確認した．直腸GISTと前立腺癌の合併は稀であるが，腹腔鏡および経肛門操作の併用にて，機能温存を図りつつ根治切除することが可能であった．

A 64-year-old man underwent detailed examinations for prostate cancer. Magnetic resonance images of the pelvis demonstrated a 14-mm submucosal tumor located between the prostate and left anterior wall of the lower rectum. Transrectal biopsy revealed it to be rectal gastrointestinal stromal tumor （GIST）. We performed en bloc resection of both tumors under laparoscopic and transanal surgery to avoid exposure and implantation to the operative field. The rectum was mobilized laparoscopically. Then, transanal partial resection of the rectal wall was performed with full-thickness incision so that the rectal GIST and the prostate could be united ; the resected lesion was sutured. Laparoscopic radical prostatectomy was performed to remove the tumors en bloc. Histological diagnosis indicated that the surgical margins of both tumors were negative. Coexistence of rectal GIST and prostate cancer is rare. We successfully resected both tumors without dyschezia or impairing the curability.