Hybrid resection of massive rectal gastrointestinal stromal tumor using laparoscopic and transanal approaches.

Rectal gastrointestinal stromal tumors (GISTs) are rare, and radical surgery such as abdominoperineal resection is necessary for large rectal GISTs to obtain tumor-free resection margins. Here, we describe a 77-year-old man with a locally advanced non-metastatic GIST in the left anterolateral wall of the lower rectum. Tumor size was estimated to be 73 mm, and invasion of the left seminal vesicle and prostate was suspected. Chemotherapy with imatinib mesylate reduced the tumor size, creating a slight gap between the tumor and anterior organs. Therefore, we performed sphincter-sparing partial rectal resection using a hybrid method of laparoscopic and transanal approaches. The postoperative course was uneventful, and the patient remains disease-free on adjuvant chemotherapy 12 months after surgery. This case suggests that a hybrid method of laparoscopic and transanal surgery allows oncological and function-preserving excision of large rectal GISTs.