Characteristics of gastrointestinal stromal tumors incidentally discovered during abdominal surgery.

Abstract

835 Background: Gastrointestinal Stromal Tumors (GISTs) are rare sarcomas with 5000 new cases each year. Despite their low incidence, surgeons should be familiar with this pathology since GISTs can be encountered incidentally during abdominal surgery. Methods: A retrospective series was conducted by querying pathology and operative reports from a community cancer center between 2005 and 2019 for all GIST diagnoses. Patients identified to have incidental GISTs discovered intra-operatively while undergoing surgery for another diagnosis were the focus of this study. Patient and tumor characteristics were evaluated. Results: A total of 195 patients had a diagnosis of a resected GIST during our study period. Of these 195, 48 patients were incidentally discovered to have a GIST excised during another index operation. The average age of these patients was 62 years old, 27 were female and 21 male. The primary location of these incidental GISTs in descending frequency was stomach (62.5%, n = 30), small bowel (31.3%, n = 15), colon (4.2%, n = 2) and esophagus (2.1%, n = 1). The average GIST size for the cohort was 1.7cm, with stomach, small bowel, colon and esophagus measured at 1.8cm, 1.7cm, 0.65cm and 0.30cm, respectively. Mitotic rate was < 5 mitosis/50 HPF in 96% of patients. Incidental GISTs were identified during the following surgery: colon (n = 14), bariatric (n = 13), non-bariatric gastric (n = 10), hernia (n = 4), pancreatic (n = 3), esophageal (n = 2) and other (n = 2). Most incidental GISTs were discovered during elective surgery (81.3%, n = 39) compared to emergency surgery (18.8%, n = 9), and for benign disease (n = 33) compared to malignant (n = 15). Conclusions: Approximately one quarter of all GISTs resected at our community cancer center in 15 years were discovered incidentally, and during a wide variety of abdominal surgeries for both benign and malignant disease. Almost all these GISTs were < 2cm, benign, and should be cured with the incidental resection. Abdominal surgeons should be aware of unexpectedly finding small GISTs and should not be apprehensive about resecting since they have indolent characteristics. Larger lesions should trigger expert surgical oncology consultation.