Gastrointestinal stromal tumors: are they of cajal cell origin?

Recently some reports have suggested that gastrointestinal stromal tumors (GIST) might originate from the interstitial cells of Cajal or differentiate into them because they express c-kit and/or CD34 and indicated that the majority of previously diagnosed smooth muscle tumors (SMT) actually belong to GIST, but are not true SMT. We, therefore, detected c-kit, CD34, SMA, and S-100 in 106 Chinese cases of gastrointestinal tumors, which were histopathologically diagnosed as smooth muscle tumors originally, to demonstrate the immunophenotypes of these tumors. The results showed that 73 cases had immunoreaction with c-kit and/or CD34, of which 48 cases showed coexpression with either SMA or S-100 or with both. A correlation between the immunophenotypes and known histopathological parameters was also shown here based on follow-up data. We suggest that the concept of GIST should not be used as an umbrella to cover all gastrointestinal mesenchymal tumors, but be defined in a narrow term as differing from true smooth muscle tumors.