Expression of c-kit (CD117) and Ki67 provides information about the possible cell of origin and clinical course of gastrointestinal stromal tumours

Aims: Gastrointestinal stromal rumours (GIST) were analysed to determine th eir immunophenotype with emphasis on the expression of CD34 and c-kit and t o identify a possible cell of origin. Furthermore, the aim was to correlate clinical, histological and immunophenotypic parameters to their clinical c ourse by means of statistical analysis. Methods and results: An immunohistochemical analysis was performed on 64 ca ses of GIST. Three of the tumours displayed an immunohistochemical phenotyp e compatible with the diagnosis of leiomyomatous tumour. Almost half the tu mours were stained positively for CD34 and 48 of 61 tumours were positive f or c-kit (CD117), a marker of haematopoietic progenitor cells, mast cells a nd the so-called interstitial cell of Cajal (ICC), In most of the cases, th e staining was strong and evenly distributed within the rumours. Statistica l analysis on 31 cases with an appropriate follow-up time, showed that the expression of Ki67 in the nuclei of the tumour cells was the most important prognostic factor. Conclusions: Judging from the results of the immunohistochemistry there wou ld appear to be some justification for suggesting a label of ICC tumours fo r these c-kit-positive tumours without any other obvious phenotype, A discr iminant function analysis allowed 90.3% of patients to be correctly classif ied in prognostic terms from data on Ki67 and CD34 expression, grade, size and patient age.