PURPOSE: Paraffin-embedded tissue samples from the gastrointestinal tract, which had been diagnosed as tumors of a mesenchymal origin, were reviewed by an immunohistochemical staining method. The prognostic significances of the immunohistochemical
subtypes and anatomical locations were also investigated. GIST, as a new grading system, was compared with the pre-existing system for its useful prognostic significance. METHODS: 122 cases were evaluated and classified by immunohistochemical staining
for KIT, CD34, actin, desmin, vimentin, S-100 protein and NSE. RESULTS: Positivity for both KIT and CD34 of 92.6 and 73.8%, respectively, indicated that KIT was more effective for the diagnosis of GISTs. The stomach (62.3%) and small bowel (23.7%) were
most common organs of GIST. There was no difference in the prognosis between these two organs. Immunophenotypically, the uncommitted, myoid, combined and neural types were 37.7, 23.7, 20.2 and 7%, respectively. There was no significant difference in
the
prognosis between these types. The old grading system showed no difference between the borderline and malignant groups (P=0.14), whereas, the new grading system showed a significant difference between the intermediate and high risk groups (P=0.01).
CONCLUSION: KIT is more useful for the diagnosis of GOSTs. The immunophenotypical classification and anatomical location showed no prognostic significance in GISTs. Therefore, the new grading system might be more useful than older system.
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