Revision of gastrointestinal mesenchymal tumours with CD117

Background. Tyrosinekinase inhibitors improve the treatment of gastrointestinal. stromal. tumours (GISTs) and their diagnosis has been facilitated by recently developed immunohistochemical. markers. It is hypothesised that in the past, the true incidence of GISTs has been underestimated. Aims. To study the clinicopathological features of previously resected mesenchymal. tumours of the gastrointestinal tract and determine the accuracy of previous diagnostic results. Patients and methods. Patients with mesenchymal. tumours of the gastrointestinal tract operated on between 1987 and 2002 were identified using medical and pathologic files. Immunohistochemical. staining for CD117, CD34, desmin and S100 was performed, and diagnosis reviewed. Results. Thirty-six mesenchymal. tumours were reanalysed. Before revision, diagnosis of GIST was correctly made in only six cases. Supportive use of immunohistochemical markers for accurate diagnosis of the remaining 30 previously undefined mesenchymal. tumours yielded 17 additional GISTs. Therefore, 23 of 36 (63%) gastrointestinal mesenchymal. tumours were shown to be GISTs. Conclusions. The true incidence of GISTs has been underestimated. There is merit in reviewing the clinical diagnoses of all. mesenchymal. tumours of the gastrointestinal tract with modern immunohistochemical. markers. This may enhance clinical. decision making. (C) 2004 Elsevier Ltd. All rights reserved.