Intestitial Cells of Cajal in the Human Small Intestine: Immunochemical and Ultrastructural Study

The stem cell kinase CD117 has recently been found to play an important role in the development of interstitial cells of Cajal (ICC), which are currently regarded as pacemaker cells of the gastrointestinal tract. CD117 is expressed in both gastrointestinal stromal tumors (GIST) and ICC, with the latter regarded by many as the progenitor cells of GIST. The authors investigated immunoreactivity of 25 normal surgically removed small intestinal tissues and correlated the findings with electron microscopy (EM) on 12 cases. In all cases CD117-positive cells were frequently seen around the myenteric plexi either singly or in groups. CD117-positive cells on immunostained sections corresponded to the cells appearing as fibroblast-like or undifferentiated primitive mesenchymal cells around the myenteric ganglia and interstitial spaces by EM. In contrast, S-100 stain revealed a fine network of positive staining throughout the muscularis. Branches of nonmyelinated axons and nerve endings were found regularly between ...