Primary Extragastrointestinal Stromal Tumor of Retroperitoneum: Poor Response to Tyrosine Kinase Inhibitor

ABSTRACT

Gastrointestinal stromal tumors (GIST) are the most common sarcomas arising in the gastrointestinal tract. Stromal tumors arising outside the gastrointestinal tract are known as extragastrointestinal stromal tumors (EGIST). EGISTs may occur in omentum, mesentery, or retroperitoneum and are histologically and immunophenotypically similar to that in GISTs. EGISTs are very rare, so pathogenesis, incidence, and prognosis of EGISTs are not defined yet. In particular, there are a few reported literatures on the treatment of metastatic EGISTs. I report a case of a primary EGIST of the retroperitoneum with lung metastasis surgically removed and treated with tyrosine kinase inhibitor.