| [ Summary ] |
Gastrointestinal stromal tumors (GIST) are currently considered to derive from interstitial cells of Cajal (ICC). However, there have been some reports that mesenchymal tumors, primarily in extra-gastrointestinal sites, such as the omentum, the mesentery, the pelvic cavity, the liver and the retroperitoneum, were also immunoreactive for KIT. Some of these showed c-kit gene mutations. However KIT-positive ICC have not been observed in these sites. These tumors are known as extra-gastrointestinal stromal tumors (EGIST) and the development of EGIST cast doubt on ICCs as the origin of GIST. However, we discovered KIT positive ICC-like cells just beneath mesothelial cells in the omentum. Moreover, the primary sites for EGIST in previous reports were limited to the abdominal region. These results indicate that KIT-positive bipolar mesenchymal cells may be counterparts of ICCs in the GI tract and EGIST may develop from those ICC-like cells. Further studies will be needed to understand the developmental origins of EGIST. |