Extra-Gastrointestinal Stromal Tumor with Complications and Disease Progression: Case Report and a Brief Review of the Literature

Gastrointestinal Stromal Tumors (GISTs), derivatives of the Interstitial cells of Cajal, are the most common mesenchymal tumors of the gastrointestinal tract. Extra-gastrointestinal stromal tumors (EGISTs) are a subtype of GIST that represent less than 5% of all GISTs. EGIST arises either in the mesentery, omentum, or in the retroperitoneum, regardless of the gastrointestinal wall. Similar to GISTs, EGISTs are typically associated with mutations that result in gain of function in the KIT or PDGFRA receptor tyrosine kinase genes. Most EGISTs are found in the omentum and mesentery, and since they grow large in the abdominal cavity, most of them are large and palpable tumors. They are histologically defined as spindle or epithelioid cells, which are usually positive for CD117 (KIT) and DOG1.EGISTs are rare mesenchymal neoplasms that pose a significant clinical challenge due to their potential for aggression and a tendency to recur. We report a case of a high-risk, large mesenteric EGIST that had exhibited a complicated clinical course. The case went through an intraoperative tumor rupture, adjuvant treatment with imatinib, recurrence, and progression with increasing dose and second-line sunitinib treatment. EGISTs are more likely to have an aggressive clinical course and recurrence than GISTs of the same size and mitotic rate; therefore, aggressive treatment and long-term follow-up are needed.This case illustrates the impact of unfavorable prognostic factors, particularly tumor rupture and R1 resection, on the long-term prognosis of high-risk EGIST. It highlights the need for aggressive, multidisciplinary management, extended adjuvant therapy, and the challenges associated with managing sequential resistance in advanced EGIST treatment.