A Case of Rectal Gastrointestinal Stromal Tumor Resected by Transanal Total Mesorectal Excision after Neoadjuvant Imatinib Treatment

Abstract

A 62-year-old man presented to a local hospital with constipation. A tumor above the anal verge was identified through a digital rectal examination, and the patient was diagnosed with a rectal gastrointestinal stromal tumor (GIST) using endoscopic ultrasound-guided fine-needle aspiration. A 50 mm tumor was adjacent to both the prostate gland and levator ani muscle, and radical surgery following neoadjuvant imatinib treatment was planned. Six months after imatinib treatment, the tumor shrank to 39 mm, and the borders between the tumor and the prostate gland and between the tumor and levator ani muscle were clearly distinguished. The patient underwent laparoscopic low anterior resection with transanal total mesorectal excision (taTME). The tumor was completely resected without any pseudo-capsule injuries, and the density of tumor cells in the resected specimen was significantly reduced compared to that before imatinib treatment. The patient had no local recurrence or distant metastasis a year and three months after surgery. Rectal GIST surgery is often challenging because of the enormous size of the tumors in the narrow pelvis ; thus, extended surgery is often performed. Here, we report a case of rectal GIST completely resected using taTME without any complications after neoadjuvant imatinib treatment, along with a literature review.