CD34 immunoexpression in stromal tumours of the gastrointestinal tract and in mesenteric fibromatoses.

The aim of this study was to explore whether CD34 immunoreactivity can distinguish between different types of gastrointestinal stromal tumour, i.e. smooth muscle and neurogenic. We studied 87 stromal tumours from different sites in the gastrointestinal tract, as well as the omentum and mesentery, using a monoclonal antibody to CD34 (QBEND10). We also determined the immunoexpression of smooth muscle and muscle specific actins, S-100 protein, cytokeratin, desmin and vimentin. In addition, 15 cases of mesenteric fibromatosis were tested for CD34. Immunoexpression of CD34 was observed in 40 of the 87 stromal tumours and correlated with evidence of differentiation towards a smooth muscle phenotype. Large intestinal stromal tumours were less likely than gastric lesions to be CD34 positive. None of 15 cases of mesenteric fibromatosis was positive for CD34. We conclude that CD34 immunoexpression is seen in a proportion of stromal tumors of the gastrointestinal tract, mesentery and omentum, particularly those of smooth muscle type, and it may be useful as part of an immunohistochemical panel in the differential diagnosis of these neoplasms.