Is gastrointestinal stromal tumor (GIST) originating from the rectovaginal septum GIST or extra-GIST (EGIST)? A case report with literature review.

Gastrointestinal stromal tumors (GISTs) are rare tumors of the gastrointestinal (GI) tract that arise from primitive mesenchymal cells. Extragastrointestinal stromal tumors (EGISTs) are extremely rare tumors that show the features of GISTs outside the GI tract. Their most common locations are the omentum, mesentery, and retroperitoneum. The authors report herein a case of a 54-year-old woman with GIST in rectovaginal septum. The patient underwent low anterior resection of the rectum, total abdominal hysterectomy, bilateral salpingo-oophorectomy, and partial resection of the posterior vagina. She received adjuvant therapy with an oral tyrosine-kinase inhibitor. She is presently healthy without any evidence of recurrence at 26 months after surgery. For GISTs arising in the rectovaginal septum, it is difficult to ascertain whether the tumor origin site is the rectum, rectovaginal septum, or vagina. In other words, it is difficult to classify these tumors as GISTs or EGISTs. More consideration for the exact origin should be given to the GIST in the rectovaginal septum for the precise diagnosis (GIST or EGIST) and risk classification in future.