<prompt> A 50-yr-old male presents with obstructive symptoms. Biopsy of stomach reveals Gastrointestinal stromal tumor GIST. Most appropriate marker for GIST is:CD 34CD 117CD 30CD 10  <response>: GISTs express the Kit CD117, stem cell factor receptor protein. The kit is a transmembrane tyrosine kinase receptor. The Kit protein is detected by immunohistochemistry and can reliably distinguish GISTs from true smooth muscle neoplasms.Most GISTs also are positive for CD34, a hematopoietic progenitor cell antigen.KIT is used not only for diagnosis but also for targeted therapy of GISTs. Imatinib, a tyrosine kinase inhibitor, is widely used in the treatment of advanced and metastatic GISTs and has been recently employed in the neoadjuvant and adjuvant set-up with encouraging results. 