Fibroid polyps of intestinal tract are inflammatory-reactive proliferations of CD34-positive perivascular cells

Our aim was to determine the histogenesis of fibroid polyps (FP). These polyps are rare inflammatory-reactive, tumour-like lesions of unknown aetiology, arising in the submucosa or mucosa of the gastrointestinal tract. They are mainly due to a proliferation of characteristic spindle cells.

Nine FP were investigated by light microscopy and immunohistochemistry with endothelial markers (Factor VIII, CD34, CD31), a neuronal marker (S100), muscular markers (desmin, alpha-smooth muscle actin) and histiocytic markers (PGMI, KP1, MAC387) using the highly sensitive avidin-biotin-peroxidase technique. We demonstrate, for the first time, a consistent positivity of the characteristic spindle cells of FP for CD34. The proposed endothelial, histiocytic or neuronal origin of FP could be completely ruled out.

Because of the consistent positivity of the spindle cells of FP for CD34 we suggest an origin of these lesions from primitive perivascular or vascular cells. This origin and a probable relationship to gastrointestinal stromal tumours (GIST) is discussed.