The paper gives the results of treatment in 19 patients with gastrointestinal stromal tumors more than 10 cm in the least measurement. The largest tumors measured 45 cm. Surgery was performed in 17 patients; 11 and 6 patients had radical and palliative operations, respectively. All tumors had a profuse blood supply from the bed of large blood vessels of abdominal organs and from the newly formed vessels connected to the abdominal wall circulatory system and iliac vessels. At the first stage of treatment, external drainage of a decay cavity was carried out in 3 patients. There were no fatal outcomes in the postoperative period. Seventeen patients received targeted therapy. Long-term results were traced in 14 of the 19 patients. The mean follow-up period was 14.7 months. Two patients died from disease progression; the remaining patients are alive to the present day.