Robot-Assisted Laparoscopic Resection With the Transanal Approach for Massive Rectal Gastrointestinal Stromal Tumor: A Case Report.

Rectal gastrointestinal stromal tumors (GISTs) are often asymptomatic and may be detected as giant tumors. This may require highly invasive surgery for radical resection. Here, we describe a 74-year-old man with a locally advanced non-metastatic GIST in the right anterolateral wall of the lower rectum. The tumor was giant (128 × 93 mm), and invasion into adjacent organs (right seminal vesicle and prostate gland) was suspected. Although neoadjuvant chemotherapy (NAC) with imatinib reduced the tumor size, it was still giant, 80 mm in diameter. Therefore, we performed super-low anterior resection using a robot-assisted laparoscopic approach with the transanal approach. The bi-directional approach enabled safe and precise surgery, is expected to increase the rate of anorectal preservation as well as R0 resection, and may prevent a decline in quality of life.