Transvaginal ultra-low anterior resection for low rectal gastrointestinal stromal tumor after neoadjuvant imatinib: a case report

Rectal gastrointestinal stromal tumors (GISTs) are uncommon and their low pelvic location makes complete resection with preservation of the anal sphincter technically challenging. Neoadjuvant imatinib may facilitate organ-preserving surgery. We report a transvaginal ultra-low anterior resection for a low anterior rectal GIST in a woman. A 45-year-old woman presented with bleeding per rectum. Digital rectal examination revealed an anterior rectal wall lesion with distal lesion extending to approximately 4 cm from the anal verge. Colonoscopy showed an ulcerated submucosal growth at the anorectal junction. Biopsy demonstrated a GIST positive for CD117 and DOG1, with a reported mitotic index of 3/50 high-power fields. After 6 months of imatinib 400 mg daily, imaging demonstrated approximately 50% reduction in tumor dimensions. Pre-operative MRI showed a well-defined exophytic T2 hyperintense lesion 5×4×3 cm in anterior wall of mid and lower rectum projecting into recto-vaginal space. Lowermost point of contact is 2,5 cm from anal verge, displacing the cervix and vagina anteriorly with preserved fat planes. Anal canal and sphincter complex appear uninvolved. Pelvic side walls appear free. At operation, a 5×4×3 cm circumscribed submucosal distal rectal tumor was identified, with a partly exophytic component impinging on the vagina. Following abdominal mobilization and proximal rectal transection, the posterior vaginal wall was incised and the distal rectum was transected with a reported 1-cm distal margin. The specimen was retrieved transvaginally and a coloanal anastomosis was constructed using interrupted 2-0 Vicryl sutures. The vaginal mucosa was closed with 2-0 Vicryl and a diverting ileostomy was created. Final histopathology showed spindle-cell GIST, mitotic index of 3/50 high-power fields with free proximal and distal margins and reported pT3N0 stage. The patient continued postoperative imatinib. A rectovaginal fistula developed at 6 months, was surgically repaired and healed. Ileostomy closure was performed 2 months later. At 14 months of follow-up, she remained well with unremarkable bowel and bladder function. In carefully selected women with a low anterior rectal GIST, a transvaginal route can provide direct access to the distal rectum and may facilitate sphincter-preserving resection. Further experience and longer follow-up are required to establish its oncological and functional outcomes.