Clinicopathological features of gastric inflammatory myofibroblastic tumor: Report of five cases.

The present study reported on the histomorphological observations and immunohistochemical features of five cases of gastric inflammatory myofibroblastic tumor (IMT). Loosely arranged fat fusiform myofibroblast-fibroblasts and diffusely or patchily distributed inflammatory cells, which formed a diverse morphological structure, were observed. In the mucous vascular structure, mucoid or collagenous areas, fibromatosis- or scar-like lesions were generally <10 mm in size and both had diffuse or patchy plasma cells, lymphocytes and other inflammatory-cell infiltration backgrounds. The immunophenotype was vimentin- and smooth muscle actin-positive with pan-cytokeratin, desmin and calponin expression and CD34-positive foci; furthermore, three cases were positive for anaplastic lymphoma kinase expression. Gastric IMT is rare, with unique histopathological changes and corrosion-like invasion of the smooth muscle of the stomach wall, blood vessels, nerves and adipose tissue. It should be differentiated from a variety of spindle cell tumor types and tumor-like lesions.