Classification of gastrointestinal soft tissue tumors (stromal tumors)

Gastrointestinal mesenchymal tumors traditionally have been designated as smooth muscle tumors. However, with increasingly accurate analytic tools most investigators were unable to demonstrate true myogenic differentiation. Diagnostic criteria and grading vary among different studies and the biological behaviour of these gastrointestinal stromal tumors (GIST) is difficult to predict. In this manuscript the recent concept of GIST is reviewed, including a suggestion for tumor classification. Furthermore, MIB-1 and p53 immunohistochemistry and myogenic differentiation were evaluated as potential prognostic factors. Diagnosis requires the use of immunochemistry. Classification as GIST seems appropriate, since only few tumors show complete myogenic differentiation. Besides a tumor size over 5 cm, mitotic rate still seems to be the best predictor of treatment failure in tumors that are resected with a rim of uninvolved tissue. MIB-1 proliferation index above 4% and p53 positivity indicate a more aggressive course.