Inflammatory fibroid polyps of the gastrointestinal tract. An immunohistochemical and electron microscopic study.

Seven cases of inflammatory fibroid polyp (IFP) are studied, two of them with electron microscopy. The morphologic findings suggest a myofibroblastic origin for the proliferating cells. Other histogenetic hypothesis which propose a neural or vascular nature for this lesion are ruled out. The ultrastructural features of the proliferating cells are different from schwann and endothelial cell tumors. Moreover, the immunohistochemical technique to detect Factor VIII related antigen was negative in the intercapillary cells of the seven cases. Our conclusion is that inflammatory fibroid polyp of the gastrointestinal tract represent a reactive lesion of myofibroblastic nature.