Primary Omental Gastrointestinal Stromal Tumor-What We Know and How Can We Deal With it, Based on Case Series and Review of Literature

Abstract

Gastrointestinal stromal tumors (GIST) are considered uncommon mesenchymal spindle-cell or epithelioid neoplasm, featuring Cajal cell-like differentiation; arise in high frequency from the stomach or small bowel. GISTs represent the majority of primary non-epithelial tumors of digestive tract, most frequently expressing the KIT protein a transmembrane tyrosine kinase receptor for stem cell factor and KIT/PDGFRA mutation. A small percentage of GISTs originate from extragastrointestinal masses like omentum, mesentery, and retroperitoneum. These tumors are commonly named “extra-gastrointestinal GISTs” (EGIST) and tend to be present in less than 5%-10% of cases. Although the incidence of EGIST, their clinicopathologic parameters and clinical implications have yet to be defined because of the rarity of these tumors. Besides that, these neoplasms with overlapping immunohistological features, have no connection to the gastric or intestinal wall. We describe few cases of omentum compromise and all the associated features. Omentum EGIST can grow slowly and remain quite silent despite the size, which is commonly a large tumor. Immunohistological features tend to be slight different from GIST and the prognosis is generally worse. In most cases, preoperative diagnosis it is difficult to make and the surgery is needed. Moreover, the role of imatinib, the drug of choice in the treatment of this disease, it´s still unclear in EGIST. Alternative therapies are on the field showing good results.