Immunohistochemical Expression of CD117, CD34, Vimentin and alpha-Smooth Muscle Actin in Gastrointestinal Stromal Tumors

ABSTRACT

BACKGROUND: The interstitial cell of Cajal (ICC), the cell of origin for gastrointestinal stromal tumor (GIST), expresses CD117 (c-kit) which is a receptor for KIT ligand in cell membranes. It is immunohistochemically positive for CD117, CD34 and vimentin, but not for alpha-smooth muscle actin (SMA). METHODS: We performed the immunohistochmical study with anti-CD117, anti-CD34, anti-VMT and anti-alpha-SMA in paraffin-embedded tissue of 28 GISTs and 19 smooth muscle tumors arising in the gastrointestinal tract, mesentery, omentum and retroperitoneum (GISMT) to determine the precise nature of GIST cells. RESULTS: The positive rates of CD117, CD34 and vimentin in extraGISTs were significantly higher than in GISMTs. The positive rate of alpha-SMA in GIST was not significantly different than in GISMTs. CONCLUSIONS: A subset of GISTs may express alpha-SMA as well as CD117 and the cell of their origin may be a ICC precursor cell which is capable of differentiating bidirectionally into ICC and smooth muscle cell. This explains why GISTs may arise out of gut where ICC is not present and that they may represent the tumors arising from ICC precursor cell present around the gastrointestinal tract.