Sphincter-saving resection by cluneal arched skin incision for a gastrointestinal stromal tumor (GIST) of the lower rectum: a case report

BACKGROUND Planning the surgical strategy for a gastrointestinal stromal tumor (GIST) at the posterior wall of the lower rectum is difficult, as the procedures for the lower rectum are hampered by poor visualization and may cause anal dysfunction or discomfort. We report a novel procedure to resect a submucosal tumor of the rectum. CASE PRESENTATION A 75-year-old woman presented with metrorrhagia. Endovaginal ultrasonography showed a low echoic tumor. Computed tomography showed an enhanced tumor, measuring 5.3 × 4.2 cm, behind the rectum. Magnetic resonance imaging revealed a submucosal tumor of the rectum, measuring 5.3 cm at its greatest dimension. Colonoscopy showed that the distal tumor margin was 1 cm above the dentate line. Core needle biopsy of the tumor revealed the rectal GIST. After receiving neoadjuvant imatinib treatment, the tumor size decreased to 3.5 cm. During the operation, we approached the rectum and resected the posterior rectal wall, including the 3.5 × 3.5 cm tumor with a safety margin, making an arched incision at the buttocks to form a skin flap with the patient in a jackknife position. The histopathological diagnosis was GIST of the rectum. Her anorectal sphincter function was well preserved. No recurrence was seen during the 2-year follow-up. CONCLUSIONS This novel approach improves the operative field visibility in resecting a tumor with a safety margin and preserves a patient's anorectal sphincter function.