A Metastatic Rectal Gastrointestinal Stromal Tumor to the Small Bowel Mesentery Treated with Neoadjuvant Imatinib and Debulking Surgery Followed by Low Anterior Resection

摘要

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. They arise from intestinal pacemaker cells, also known as interstitial cells of Cajal. They are identified by the expression of KIT cellular markers, also known as CD117. KIT is a proto-oncogene that gives rise to a constitutively active tyrosine kinase receptor. GISTs are most commonly found in the stomach (50-60%), small intestine (30-40%), and rectum (5%). Incidence is estimated to be around 4000 to 5000 cases per year in the United States, and median age at diagnosis is 60 years. Malignant potential is based on size and mitotic index, with the greatest risk for malignancy in tumors >10 cm and with >5 mitoses per 50 high power field (hpf). Metastatic GISTs are uncommon, with the most common site of distant spread being the liver.