Transanal total mesorectal excision for a large leiomyosarcoma at the lower rectum: a case report and literature review

BACKGROUND Rectal leiomyosarcoma (LMS) is an extremely rare disease. Previously, LMS was not properly distinguishable from gastrointestinal stromal tumor (GIST) until c-kit, a characteristic marker of GIST, was discovered in 1998. No standard therapeutic strategy for gastrointestinal LMS has been established except for surgical resection because of its rarity. Rectal LMS is often accompanied by symptoms, which can enable detection at a small size. However, when a large LMS is detected at the lower rectum, it is difficult to excise due to the narrow pelvic space. CASE PRESENTATION We present the case of an 86-year-old man with a large LMS. The LMS was asymptomatic and incidentally found at the lower rectum when he visited another hospital for management of benign prostatic hypertrophy. An abdominoperineal resection of the rectum was performed with combined resection of both seminal vesicles and a part of the prostate because tumor invasion was suspected. We used the hybrid method of laparoscopic and transanal total mesorectal excision (TaTME) approaches to achieve negative surgical margins. Late-onset urethral injury occurred in the postoperative course, which was successfully treated with a urethral catheter. The patient was discharged and received no adjuvant therapy. Local recurrence did not occur, but multiple lung metastases were detected 4 months later and the patient died 12 months after the surgery. CONCLUSIONS This is the first report of the hybrid method of laparoscopic and TaTME approaches to remove a large LMS at the lower rectum.