Gastrointestinal stromal tumors: usefulness of immunohistochemistry, flow cytometry and fluorescence in situ hybridization.

Background And Aims: Gastrointestinal stromal tumors (GIST) constitute a group of primary mesenchymal tumors of the gastrointestinal tract, known for their diversity in clinical behavior and the difficulties in determining malignancy and prognosis. This retrospective study evaluated a series of GIST by means of immunohistochemical techniques, flow cytometry and fluorescence in situ hybridization (FISH).

Methods: Nine patients with GIST were analyzed for tumor size, mitotic count and CD117, CD34, MIB-1 with immunohistochemistry. In addition, the GIST were tested with FISH for chromosomes 8 and 17 and DNA index was evaluated by flow cytometry.

Results: The findings confirmed the usefulness of CD117 and CD34 in diagnosing GIST and the prognostic role of MIB-1, but do not support a correlation between aneuploidy in flow cytometry and poor outcome. The FISH results suggest close follow-up for patients with benign GIST with a numerical alteration of chromosome 8. The technique could select patients with tumors at high-risk with aneusomy of chromosome 17.

Conclusion: This study shows the possible application of FISH to the evaluation of patients with GIST, in addition to analysis of morphological features.