CD34 EXPRESSION BY INFLAMMATORY FIBROID POLYPS OF THE STOMACH

The phenotype of the proliferated spindled cells and the histogenesis of inflammatory fibroid polyp (IFP) have been a matter of debate, To c larify the immunohistochemical profile of the main cellular component, we reviewed histologically and studied immunohistochemically 11 cases (12 lesions) of IFP of the stomach, The lesions ranged in size from 0 .4 to 3.0 cm (mean, 1.0 cm), All of the IFPs occurred in the antrum, S even cases (63.6%) were accompanied by carcinoma or adenoma, which in two cases was present in covering epithelium, Grossly, eight IFPs were sessile, and four were polypoid, Microscopically, seven (58.3%) occup ied both the mucosa and submucosa Four (33.3%) were confined to the mu cosa, and one was localized only in the submucosa They were characteri zed by proliferation of relatively uniform spindled cells, often in a whorl-like arrangement around the blood vessels and glands, Eosinophil ic and lymphocytic infiltration of varying degree was always present, The spindled cells in all of the IFPs were diffusely immunoreactive fo r vimentin and CD34. Seven (58.3%) were focally positive for histiocyt ic markers, such as KP1 and HAM56, Three (25%) showed focal immunoreac tivity for alpha smooth muscle actin. Cytokeratin, desmin, S100 protei n, Factor VIII RAG, and Ki-67 were negative in these spindled cells. T he principle proliferating cells in IFPs in this study showed variable degrees of histiocytic and myofibroblastic lines of differentiation. Under the influence of some etiologic factors, the primitive, uncommit ted spindled mesenchymal cells exhibiting CD34 immunoreactivity around the blood vessels and glands in the lower portion of mucosa and submu cosa might play a role in development of IFP.