label: Gastrointestinal Stromal Tumor
label_lc: gastrointestinal stromal tumor
description: "A stromal tumor most commonly seen in the gastrointestinal tract. Rare cases of solitary masses in the omentum or the mesentery have also been reported (extragastrointestinal gastrointestinal stromal tumor).  It is a tumor that differentiates along the lines of interstitial cells of Cajal.  Most cases contain KIT- or PDGFRA-activating mutations. Until recently, surgery has been the only effective therapy for this tumor.  However, many patients still experience recurrence.  Conventional chemotherapy and radiation therapy have been of limited value.  A KIT tyrosine kinase inhibitor, imatinib mesylate (also known as STI-571 or Gleevec), is now effective in the treatment of relapsed and unresectable cases."