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

Abstract

Gastrointestinal stromal tumours (GIST) were analysed to determine their immunophenotype with emphasis on the expression of CD34 and c-kit and to identify a possible cell of origin. Furthermore, the aim was to correlate clinical, histological and immunophenotypic parameters to their clinical course by means of statistical analysis. An immunohistochemical analysis was performed on 64 cases of GIST. Three of the tumours displayed an immunohistochemical phenotype compatible with the diagnosis of leiomyomatous tumour. Almost half the tumours were stained positively for CD34 and 48 of 61 tumours were positive for c-kit (CD117), a marker of haematopoietic progenitor cells, mast cells and the so-called interstitial cell of Cajal (ICC). In most of the cases, the staining was strong and evenly distributed within the tumours. Statistical 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. Judging from the results of the immunohistochemistry, there would appear to be some justification for suggesting a label of ICC tumours for these c-kit-positive tumours without any other obvious phenotype. A discriminant function analysis allowed 90.3% of patients to be correctly classified in prognostic terms from data on Ki67 and CD34 expression, grade, size and patient age.